chap2

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toc **Chapter 2**

What Do You See?
Page 132, November 19th, 2010 I see soccer players kicking soccer balls. The player who has a running start kicks the ball further than the player who kicks the ball with no running start. The running player kicks the ball over the net, and the standing player kicks the ball and it doesn't even reach the goal.

What Do You Think?
Page 132, November 21st, 2010 Figure skaters can move across ice at high speeds with little to no effort because the ice that they are on has very little friction, which lets them move for longer distances without slowing down much. A soccer ball keeps moving across the field after it has been kicked because the energy of the kick causes the ball to keep moving, with the friction in the field slowly causing the ball to slow down until it comes to a stop.

Checking Up
Page 138, November 21st, 2010 1. Inertia is the natural tendency for an object to remain at rest or remain in a constant speed in a straight line in the absence of outside forces. 2. Newton's first Law of Motion states that in the absence of an unbalanced force, an object at rest remains at rest, and an object already in motion remains in motion with constant speed in a straight-line path. 3. Forces, such as friction, must act on an object to stop it from moving at a constant-speed. 4. The friction between the rolling ball and the ground that it is traveling over slowly brings the ball to a stop. 5. The object with the greater mass will have the greater interia. 6. The frame of reference is important because there can be multiple answers. One could have one answer for the speed with a frame of reference being the train, and have another answer with the frame of reference being the ground.

Physics To Go
Page 139-141, November 21st, 2010 1a. The ball will travel in a straight line forever. 1b. The ball will travel in a straight line forever because an object in motion will stay in motion unless a force acts against it, since there is no friction, there is no force causing the ball to slow down. 2. 20cm 3. No, because there is no substance on Earth that is perfectly frictionless, however, space has favorable conditions because there is no gravity or other forces which would cause friction. 4. The puck leaves the stick, gliding across the ice, while still slowly losing acceleration, then it hits something, causing the inertia to be transitioned to moving in the opposite direction. 5. 2.5 m/s + 4.5 m/s = 7 m/s 6. 4.2 m/s + 10.3 m/s = 14.5 m/s 7a. 5.6 m/s + 2.4 m/s = 8 m/s 7b. 5.6 m/s - 2.4 m/s = 3.2 m/s 7c. 8 m/s 8. 103 m/s 9a. 21.2 9b. 43.9 9c. 57.9 9d. 172

Physics Plus
Page 139, November 22nd, 2010 Relative Velocity = Velocity (train) + Velocity (person) Relative to → platform Train moves at 20 m/s The person moves to the back of the train at -5 m/s Relative Velocity = 20 m/s + (-5 m/s) Relative Velocity = 15 m/s SOH CAH TOA Sin= Opp/Hyp Cos= Adj/Hyp Tan= Opp/Adj

Active Physics Plus
November 23rd, 2010, Page 139 1a. sin45 = 10/distance= 14.14cm 1b. sin30 = 10/distance= 20cm 1c. 29cm 3a. sin10=10/distance= 57.58 cm 3b. sin1=10/distance= 572.99cm 3c. sin.1 = 10/distance= 5729.58cm 3d. sin.01=10/distance= 57295.78cm 4. An object in motion has a certain amount of energy, and without any outside forces, all of the energy will be incorporated into motion.

Investigate 2
November 30th, 2010, Page 146 1a. There is an equal distance between all dots. 1b. The distance between the dots is smaller. 1c. The distance between the dots is larger. 1d. The dots will gradually accelerate and become farther apart from one another. 6a. 7a. If there is a constant speed, the dots will all be an equal distance away from each other as the tape is moving at the same speed. 7b. Most of the tape had somewhat of a constant speed. 8a. 8b. The speed was increasing. 8c. The speed increases. 9a. 9b. The acceleration was exponential. 10a. 10b. It will get smaller. 10c. No, the acceleration decreased exponentially. 11a. As it speeds up, the distance will get longer, as it slows, the distance will get shorter.

Checking Up
1a. If the speed is constant, the dots will be at an equal distance away from each other. 1b. The distance between the dots will gradually grow larger. 1c. The dots would become closer together. 2. 400/50 = 8 3. An average speed is the speed over a period of time, instantaneous speed is the speed at a certain point in time. 4. 10m/s

**Physics To Go**
December 5th, 2010, Page 154 1. Average speed is the speed of an object over a trip, or long period of time, and instantaneous speed is the speed of an object at an exact moment in time. 2a. .066km/s 2b. 14m/s 2c. 4.8km/hr 2d. 88.8km/hr 3a. Negative acceleration 3b. Positive acceleration 3c. No acceleration 3d. Negative acceleration 3e. No acceleration 3f. No acceleration 4a. D 4b. B 4c. A 4d. C 4e. A- Positive acceleration B- No acceleration C- Positive then Negative acceleration D- Positive acceleration 5. ﻿6a. The vehicle accelerated at 6m/s. 6b. The vehicle underwent negative acceleration. 7a. Constant 7b. Positive acceleration 7c. Positive then negative acceleration 7d. Negative, constant, then positive acceleration 8. 50mi/hr 9. No, their instantaneous speed was different, the average speed is an average, so the persons instantaneous speed could've been higher or lower than 15m/s. 10. - - - - - - - - -  11. 20m/s 12. Yes 13. The runners have to travel smaller distances so they can use more energy than someone who must conserve energy when going longer distances. 14a. Dots spaced evenly. 14b. Dots spaced farther away from each other. 14c. Dots spaced closer to each other. 14d. Dots that gradually get father away from each other. 14e. Dots that gradually get closer to each other.
 * Time Interval || Average Speed ||
 * 0.1s || .7 cm/s ||
 * 0.2s || 10.5 cm/s ||
 * 0.3s || 11.6 cm/s ||
 * 0.4s || 12.25 cm/s ||
 * 0.5s || 12.6 cm/s ||
 * 0.6s || 12.8 cm/s ||
 * 0.7s || 13 cm/s ||
 * 0.8s || 13.12 cm/s ||
 * 0.9s || 13.36 cm/s ||
 * 1s || 13.5 cm/s ||

**What Do You Think? 3**
November 29th, 2010, Page 157 A force is energy exerted on an object which causes movement, a push or pull. The same amount of force will have different effects on a tennis ball and a bowling ball because a bowling ball is heavier, and will move less than a tennis ball does with the same amount of force.

**Investigate 3**
November 29th, 2010, Page 158 2a. The car accelerates exponentially. 3a. The car accelerates more quickly. 3b. Both times the car accelerates quickly. 3c. The larger the bend, the larger the force applied to the car, which makes it accelerate at a faster rate. 3d. The greater the constant force pushing on an object, the faster the object will accelerate 4a. The object with a greater weight will accelerate slower. 5a. The car with a heavier weight attached will accelerate at a slower pace than the car with a lighter weight attached. 5b. When equal amounts of a constant force are used to push objects having different masses, the more massive object accelerates slower. 6a. The conclusion would be that the smaller object accelerates faster. 8a. There is a small bend observed in the ruler, showing that there is only a small force exerted. 9b. 20g represents a small force, 50g represents a large force. 9c. The force of gravity acting upon the ruler.

Summary
December 5th, 2010, Page 160 Newtons Second Law: Acceleration=Force/Mass. Accelerations are caused by unbalanced forces. Acceleration gets smaller as the mass gets bigger. Weight is the force of gravity acting upon an object. Weight = Mass/Gravity. Free-body diagrams diagram the forces acting upon objects.

Checking Up
December 5th, 2010, Page 167 1. The acceleration of an object is determined by the mass of the object and the force applied to it. 2. The larger the mass gets, the less the acceleration will be. 3. 30N = Mass/9.8m/s (gravity), 30N times gravity is the mass of the object. 4. Your mass would stay the same, your gravity would change, and you would start to weigh more than you do on Earth.

Physics To Go
December 5th, 2010, Page 171 1. Sprinter beginning 100m dash- Force= 350N Long jumper in flight- Mass=80kg Shot-put ball in flight- Acceleration= 10m/s Ski jumper going downhill before stopping- Mass= 80kg Hockey player stopping- Acceleration= -15m/s Running back being tackled- Force= -3000N 2a. It matches twice, they are both due to gravity. 2b. The acceleration is negative because the hockey player is slowing down. The force is negative which means that it is slowing down at 1500N. 2c. Yes, because the running back is being tackled, which means that he is slowing down, so the force will be negative too. 3. 12.6m/s 4. .8N 5a. The baseball has more inertia, which would cause it to hurt someone while catching it more than another type of ball. 5b. The baseball has more mass, which would create a greater force when trying to catch it. 6. 0.98 kg 7a. 657N 7b. 67kg 8. The force exerted by the blue team was just enough to win. The red team did not exert enough force, so they lost. 9. No, the force from your hand stops acting on the ball the moment the ball stops contact with your hand. 10. The net force acting on the desk is 10N in Sara's direction. 11. The net force acting on the vehicle is 800N. 12. .17m/s

Physics Plus
Page 168, December 6th, 2010 A football player runs North at a speed of 5.0m/s. An opponent attempts to tackle him and runs into him at 3.0m/s east. Thw two latch together but keep moving as they fall down. a) What is the speed of the two during tackle? b) What is the angle of travel?

What Do You See?
Page 171, December 9th, 2010 I see a girl dropping apples, one is dropped without horizontal movement and the other is dropped with horizontal movement. The one with horizontal movement passes over a boy with a stopwatch who is recording the time it takes for the two apples to drop to the ground, probably to see if the horizontal motion has an effect on the time it takes for the apple to fall on the ground.

What Do You Think?
Page 171, December 9th, 2010 The thing that determines the amount of distance an object thrown into the air covers is based off of the amount of force that was originally applied to the object.

Physics Talk
Page 177, December 9th, 2010 A projectile is an object traveling through the air. The horizontal motion of an object does not effect its downward motion. Even though you may not believe it, horizontal motion has no effect on the downward motion of an object. A penny with horizontal motion will hit the ground in the same amount of time it takes for a penny without horizontal motion to hit the ground. With no air resistance, the horizontal motion will stay the same while the vertical motion is always changing.

Checking Up
Page 178, December 9th, 2010 1. Without air resistance, the two will reach the ground at the same time. With air resistance however, there are more forces acting upon each object which will cause them to fall at different speeds. 2. No, an objects vertical motion is always changing because gravity is an acceleration, which means that it is always getting faster. 3. The balls velocity at the highest point is 0, and the acceleration remains the same.

Physics Plus
Page 179, December 9th, 2010 1a. The horizontal force will stay the same, and the vertical force will change by the force of gravity. 1b. 2a. The vertical force will be 25m/s and the horizontal force will be 43.3m/s 2b. The vertical force will be 25m/s and the horizontal force will be 15.2m/s 2c. There are no forces acting on the object. 2d. The object is not moving.

Physics To Go
Page 182, December 9th, 2010 1. 2. 3. 4. The bullet dropped would hit the ground first, this is hard for them to believe because the bullet shot is moving extremely quickly. 5. All objects on earth are effected by gravity, therefore all objects fall at the same rate of speed. 6. An objects horizontal motion has no effect on its vertical motion because a coin dropped and a coin dropped with horizontal distance both hit the ground at the same time. 7. Both arrows A and B, without air resistance, will strike the ground at the same time due to gravity. 8. About 3.6m/s 9a. cos37=x/15 15cos37=x x=11.48m/s 9b. 22.96m/s 10a. cos45=x/12 12cos45=x x=6.3m/s 10b. 3.15m/s

What Do You See?
Page 184, December 11th, 2010 I see a soccer ball kicked vertically in the air, and then its direction is changed towards the soccer goal by another players head. The force of the ball was redirected to a different direction.

What Do You Think?
Page 184, December 11th, 2010 1. The higher the angle, the higher the object will travel. A low angle will increase the range, a high angle will decrease the range. 2. A greater launch speed will increase the range of an object opposed to one with a lower launch speed and the same angle.

Investigate
December 14th, 2010 Vavg=distance/time Vavg=(d2-d1)/(t2-t1) Vavg= (.05-0)/(.0429-0) Vavg=1.17m/s
 * = Time(s) ||= Distance(m) ||= Velocity(m/s) ||= Acceleration(m/s2) ||
 * = 0.00 ||= 0.00 ||= - ||= - ||
 * = 0.0429 ||= 0.05 ||= 1.17m/s ||= 11.04m/s2 ||
 * = 0.0755 ||= 0.1 ||= 1.53m/s ||= 10.58m/s2 ||
 * = 0.1029 ||= 0.15 ||= 1.82m/s ||= 10.37m/s2 ||
 * = 0.1270 ||= 0.2 ||= 2.07m/s ||= 10.09m/s2 ||
 * = 0.1488 ||= 0.25 ||= 2.29m/s ||= 11.06m/s2 ||
 * = 0.1687 ||= 0.3 ||= 2.51m/s ||= 9.68m/s2 ||
 * = 0.1873 ||= 0.35 ||= 2.69m/s ||= - ||

Vavg=(d3-d2)/(t3-t2) Vavg=(.1-.05)/(.0755-.0429) Vavg=1.53m/s



My Interpretation
I think that the for the most part, the data for the speed, distance, and velocity is spot on. The puzzling aspect of the experiment is the data for the acceleration. The acceleration goes down, then fluctuates at the end, which should not occur. Possible the picket fence was dropped on an angle, not a straight line, or possibly there was an error in the gate collecting the data.

Physics Talk
Page 188, December 14th, 2010 One of the two motions of a projectile is the constant speed along a straight line, and the other is downward acceleration of 9.8m/s which is the Earth's gravity. Without air resistance, the paths of all trajectories are parabolas. Objects launched with an angle of 45 degrees travel the farthest (without air resistance). Objects shot at angles which when added, equal 90 degrees, will both travel the same distance.

Checking Up
Page 189, December 14th, 2010 1. One of the two motions of a projectile is the constant speed along a straight line, and the other is downward acceleration of 9.8m/s which is the Earth's gravity. 2. For a scientific model to be accepted, the model must match reality in nature. 3. An object shot at an angle of 10 degrees and 80 degrees will both travel the same distance. The same can be said with an object shot at 20 degrees and 70 degrees. Therefore, objects shot at angles which equal 90 degrees will travel at the same distance, which would explain why an object shot at an angle of 45 degrees travels the farthest, as 45+45=90.

Physics Plus
December 15th, 2010 Imagine a ball rolls off a table and lands on the floor. __Vertical Motion__ The ball falls down a distance of "y" in time "t", as it speeds up from rest (V yi =0) at a rate of g=9.8m/s2. __Vertical Variables__ y t V yi =0 (it begins to fall down when the ball leaves the table g=9.8m/s2 Vyf is maximum upon colliding with the floor __Vertical Formulas__ y=1/2gt 2 (if V yi =0) y=1/2gt 2 +V yi t (V yi ≠0) g=(V yf -V yi )/t V yf 2=V yi 2+2gy y=1/2(V yi +V yf )t Note: V=d/t is not valid for y-direction because V is not constant. V=d/t assumes v is constant. __Horizontal Motion__ The ball moves horizontally at a constant speed (no acceleration). A distance of "x" in time "t" __Horizontal Variables__ Vx X T Remember a=0 So Vxi=Vxf __Horizontal Formulas__ V=x/t A ball is pushed such that it rolls across a table at a constant speed of 5.0m/s. The ball rolls off the table which is 75cm tall. Tha ball lands on the floor. t y =t x =t Calculating Time: y=1/2gt 2 +V yi t .75m=1/2(9.8m/s 2 )t 2 +0 t=.39s Calculating Final Velocity: g=(V yf -V yi )/t -9.8=(V yf -0)/(.39) V yf=-3.8m/s Calculating Distance  V=X/T  5=X/.39 5*.39=X 1.95m=X
 * = Variable ||= y ||= x ||
 * = distance ||= 75cm ||= 1.95m ||
 * = time ||= ?=.39s ||= ?=.39s ||
 * = Vi ||= 0 ||= 5.0m/s ||
 * = Vf ||< -3.8m/s ||= 5.0m/s ||
 * = a ||= 9.8m/s2 ||= 0 ||

Physics To Go
December 16th, 2010 1. A 45 degree angle would propel an object the farthest, because it is half vertical and half horizontal, which would give the largest distance. 2. An angle greater than 45 degrees would give a larger airtime than an angle less than 45 degrees. 3a. 60 degrees 3b. 75 degrees 4. Any angle higher than 18 is probably extremely hard to do, that is why no one jumps at a 45 degree angle. 5. He is a sprinter, which helps in jumps because the distance of a jump depends on the initial speed. 6a. Towards the ground 6b. Down and to the right 7a. g=(V yf -V yi )/t -9.8=(V yf -0)/3 V yf =29.4m/s 7b. 5m/s 7c. V=X/T x=VT x=(5)(3) x= 15m 8. An angle of 45 degrees. 9. An angle of 90 degrees would cause the projectile to travel the highest. 10a. Towards the ground. 10b. 4.5s 10c. 90m
 * = Variable ||= X Variable ||= Y Variable ||
 * = d ||= 15m ||= ? ||
 * = t ||= 3s ||= 3s ||
 * = Vi ||= 5.0 ||= 0 ||
 * = Vf ||= 5.0 ||= 29.4m/s ||
 * = a ||= 0 ||= -9.8m/s ||

What Do You See?
Page 198, January 3rd, 2011 I see the kid in the picture pushing himself with his feet, to the right off a wall, propelling himself to the left. The wall pushes on the boy, and the boy pushes on the wall, which is Newtons Third Law. The wall also stretches, or bends, because of the pressure caused by the boy, which then causes the wall to propel him in the opposite direction.

What Do You Think?
Page 198, January 3rd, 2011 Jump Instructions 1: Stand with both feet on the ground, with your legs shoulder width apart. 2: Bend both of your legs at the knee simultaneously. 3: Quickly straighten your legs, ending on your tip toes, using your body mass to propel yourself off of the ground and into the air.

Investigate
Page 198, January 3rd, 2011 1a. Motion is accelerated when someone exerts a force on the wall and pushes themselves off of it. 1b. Motion is at a constant speed when one reaches the maximum velocity for a certain push. Without friction, you should stay in motion forever. 1c. The source of the force is the push off of the wall. The wall pushes on your legs when you push on it, causing yourself to be propelled in the direction opposite of the wall. 1d. You push against the wall in the direction of the wall. 1e. The force of the wall is greater because the wall does not move, and you are propelled in the direction opposite of it. 2a. Student A travels backwards. 2b. The force of him pushing against Student B's palms forces him to travel in the opposite direction. 2c. Student B travels backwards. 2d. The force of him pushing against Student A's palms forces him to travel in the opposite direction. 3a. When running, your feet push on the ground, causing you to accelerate forward. 3b. It would be possible, but you could not run as fast as you could on a regular surface, as you cannot get the same grip. 4a. It is not possible, the weight exerted on each weight will always be equal. 4b. -> <--- Part B 3a. Nothing happens 4a. 2mm deflection 4b.100n 4c. It is deflecting a negligible amount

Active Physics Plus
Page 206, January 4th, 2011 Free Body Diagrams (FBD) A simple diagram of an object that shows the forces acting on it. Book Sitting on Table- 2 Forces: • Weight (Force of gravity, Fg) • Normal Force, Fn (The force of a surface pushing back on an object Example: Book pushes on desk (Fg); desk surface pushes on book (Fn).) According to Newtons Second Law: ∑=Net Force ∑=ma ∑(y)=ma(y) Fn-Fg=m (0) Fn=Fg Fn=mg

Book Falling (Ignoring air resistance) One force: • Weight (Force of Gravity), Fg ∑=Net force ∑(y)=ma(y) -Fg=ma(y) mg=ma(y) -g=a(y)

Pushing a book across a Table Four Forces: • Weight, Fg • Normal Force, Fn • Pushing Force, Fp • Friction Force, Ff ∑= Net Force ∑(y)=ma(y) Fn-Fg=m (0) Fn=Fg Fn=mg ∑= ma(x) Fp-Ff=ma(x) Fp=ma(x)+Ff

Object A- Fnetb=MbAb Ft=MaAa A=Ft/Ma Object B- Fp-Ft=MbAb Ft=Fp-MbA MaA=Fp-MbA MaA+MbA=Fp A(Ma+Mb)=Fp A=Fp/(Ma+Mb)=100N/4+10=100/14kg A=7.14m/s2

Physics Talk
Page 201, January 5th, 2011 Newton's third law is that for every force, there is an opposite and equal force. Every force has an opposite yet equal counter-force. Free Body Diagrams are diagrams of the forces acting upon an object. The center of mass is the exact center of any given object.

Checking Up
Page 205, January 5th, 2011 1. Newton's third law of motion is that for every applied force, there as an equal and opposite force. 2. The object that gravity is applying force to. 3. A Free Body Diagram shows the forces that are acting upon an object.

Physics To Go
Page 208, January 5th, 2011 1. Yes, the hand would need to be able to support the ball. 2. Yes, there is a deflection whenever a force is applied to an object. The chair pushes back with an equal and opposite force because the chair is able to support you, if the force is a force to great for the chair to push back, it will break. 3. The force applied to the scale causes it to deflect, and the deflect is measured in reference to weight. 4. Some areas of the bat are stronger than others, and therefore are able to withstand a higher deflection. Bats break because they cannot withstand the deflection from the force applied by the baseball. 5. The linebacker takes down the smaller player because the force applied is too much for the smaller player to withstand. However, both players withstand the same amount of force. 6. The boards deflect and exert an equal yet opposite force on the player, making sure he stays within the limits of the rink and does not go through the boards. 7. A baseball glove has a pocket which will deflect better than a persons hand. The ball hits the pocket, which exerts a force opposite of the ball better than a hand.

Ball in Cup Lab
January 5th, 2011

What Do You See?
Page 210, January 6th, 2011 A girl is trying to pull a shoe attached to a force-gage. She is doing it on ice and in the other frame in sand. She is moving quickly on the ice because there is little friction, and struggling to move when on the sand because there is a lot of friction.

What Do You Think?
Page 210 Some sports require special shoes because they are specifically made to be the best for a sport. They are created with special materials, with special features which give the ideal amount of friction for accomplishing a task. Different shoes are needed because different sports are played on different surfaces, which would require different amounts of friction.

Checking Up
Page 214 1. The force pulling on the scale is the force of friction, so the force of friction is equal to the force pulling on it. 2. The coefficient of friction has no units because it is a force divided by a force, therefore the two cancel out, making the coefficient unit-less. 3. The coefficient of friction is determined by diving the force of friction (Ff) divided by the normal force (Fn). Ff/Fn=µ

What Do You See?
Page 220, January 18th, 2011 I see a person running up to the side of a wall with a pole vault, then in the second frame/sequence, the pole vault has hit the side of the wall and is beginning to bend. In the third frame/sequence the person is using their bodies momentum to thrust themselves, along with the pole vault, up into the air.

What Do You Think?
Page 220, January 18th, 2011 I think that it is not possible because an 11m long pole would be very long and awkward to hold. The speed required to propel someone 12m would be impossible to attain. Doubling the length of the pole would not allow one to attain twice the height. I think some variables that limit the height attainable are, running speed, flex strength of the pole, height, weight, strength, and jumping ability.

Investigate 8
Page 221, January 18th, 2011 • What must be done to launch a quarter with a ruler to make it hit the ceiling? We pulled the ruler down in centimeter increments. We found that every time we increase the amount of bend in the ruler, the height attained by the quarter increased exponentially. • What happens if we double the length of the ruler? The ruler length was doubled, and we could not launch the quarter to the ceiling, we tried the same amount of bend as the first ruler, and the quarter went barely anywhere. We then doubled the amount and the quarter still did not reach the ceiling. We had to give up as the bend required would break the ruler.

Physics Talk
Page 227, January 18th, 2011 Kinetic Energy is energy associated with motion. Gravitational Potential Energy is energy associated with position. Potential Energy is the possible energy. The concept that the total energy remains constant is the law of conservation of energy. When flexing the ruler in the Investigate, the ruler had elastic potential energy, which was unleashed when one let go of the ruler. When a coin is in the air, the sum of its kinetic energy and gravitational potential energy remained constant, even though the speed and position of the coin was changing. Elastic Potential Energy= EPE=1/2kx2. k is the spring constant and x is the bending in meters. Gravitational Potential Energy= GPE=mgh. m is the mass of the object, g is the acceleration due to gravity, h is the height that the object is lifted. Kinetic Energy=KE=1/2mv2. m is the mass of the moving object, v is the speed of the object.

Checking Up
Page 227, January 18th, 2011 1. A force is required for the energy of an object to change. 2. The penny that is launched into the air gets its energy from the Elastic Potential Energy from the bend in the ruler. 3. The pole vaulter gets his energy from running, and from the Elastic Potential Energy from the bend in the pole vault. 4. The unit for work or energy is the joule.

Active Physics Plus
January 19th, 2011 Determining the spring constant (k)- Fs=-kx k=-Fs/x Fs=Fg
 * = m ||= Fg ||= x ||= k ||
 * +2kg || 1.96 || .22m || 8.90n/m ||
 * +4kg || 3.92 || .47m || 8.34n/m ||
 * +6kg || 5.88 || .72m || 8.16n/m ||
 * +8kg || 7.84 || .97m || 8.08n/m ||

EPE=1/2kx2 EPE=1/2(8.1n/m)(.97m) EPE=3.8 joules

Work is done on a spring to give it energy. Work --> converts to --> EPE --> converts to --> KE --> converts to --> GPE 1a. m=100g=.1kg h=1.20m GPE=mgh GPE= (.1)(9.8)(1.2) GPE= 1.18J

1b. The GPE came from KE, so GPE = KE GPE=1.18J=1/2mv2 1.18=1/2(.1)v2 V=4.9m/s

Physics To Go
Page 232, January 20th, 2011 1. You first lift the ball up, lifting it over the force of gravity. You do work using your arm to cause the shotput to travel. You give the shotput GPE and KE upon release. 2. You lift the gold club up, over the force of gravity. You do work to draw the club back and swing to give the golf ball GPE and KE. 3. KE=GPE 1/2mv2=mgh 1/2v2=gh 1/2(12)2=(9.8)h 7.35m=h 4. The height attained does not depend on the length of the pole, it depends on the velocity that can be attained by a vaulter. 5. When you bend an item, you are breaking the bonds in it, which causes it to heat up. 6. KE=GPE 1/2mv2=mgh 1/2v2=gh 1/2v2=(9.8)(4.55) 1/2v2=44.59 v2=89.2 v=9.44m/s 7. KE=GPE 1/2mv2=mgh 1/2v2=gh 1/2v2=(9.8)(6.14) 1/2v2=60.17 v2=120.34 v=10.97m/s 8. GPE=KE mgh=1/2mv2 gh=1/2v2 (9.8)(100)=1/2v2 1960=v2 v=44.3m/s

What Do You See?
Page 234, January 31st, 2011 I see a figure skater in the air above an ice rink, with a helicopter next to him. Circles below the figure skater show that he is spinning and "defying gravity". The person in the helicopter is timing how long the figure skater stays in the air.

What Do You Think?
Page 234, January 31st, 2011 1. No, no athlete's hang time makes them appear to defy gravity, gravity is always acting upon us and there is no way for a human to defy it. 2. No, the hang time of a figure skater can easily be explained through speed and momentum.

Investigate 9
Page 235, January 31st, 2011 1a. The skater was in the air for 20 frames. 1b. Time in air=(No. of frames)(1/30s) T=(20)(1/30s) T=20/30s T=.67 seconds The skater spent .67 seconds in the air. 1c. It seems that the player is hanging during the apex. 2a. The basketball player was in the air for 31 frames. 2b. Time in air=(No. of frames)(1/30s) T=(31)(1/30s) T=31/30s T=1.03 seconds 2c. During the apex of the jump is when the player appears to be hanging in midair. 3. Matt's weight in Newtons- 155lb*4.38N/lb=678.9N 678.9/.8=69.28N 4a. Matt's C of M in the ready position is 75cm from the ground 5a. Matt's C of M standing up is 81cm from the ground. 5b. The difference between the two is 6cm. 6a. Matt's jump reached a height of 110cm above the floor. 6b. 29cm 7a. GPE=70.3kg*9.8*.29 GPE=199.78J 7b. EPE=70.3kg*9.8*.29 EPE=199.78J 7c. GPE=70.3kg*9.8*.06m GPE=41.3J 7d.
 * =  ||= GPE ||= KE ||= EPE ||
 * = Ready ||= 0J ||= 0J ||= 0J ||
 * = Launch ||= 41.3J ||= 0J ||= 41.3J ||
 * = Peak ||= 199.78J ||= 199.78J ||= 199.78J ||

Physics Talk
Page 237, January 31st, 2011 Ready Position- When one is in a bent position to gain momentum. Launch Position- When one moves upward but doesn't leave the ground. Peak Position- The highest point one attains while in the air. 1. The energy is created when one moves their legs from bent to straight. 2. In the Launch Position, there is both kinetic energy and GPE, in the air there is only GPE. 3. Other types of energy are EPE and work.

Physics Plus
Page 242, February 3rd, 2011 A. GPE=mgh GPE=(0.050kg)(9.8m/s2)(.45m) GPE=.221J

KE=1/2mv 2 KE=1/2(.050)(0) KE=0J because V=0

ET=KE+GPE ET=0+.221 ET=.221J V=0
 * ET never changes because FF=0

B. GPE=0 because h=0

KE=ET-GPE KE=.221-0 KE=.221J

KE=1/2mv2 .221=1/2(.050)v2 V=3.0m/s

C. GPE=(.050)(9.8)(.28) GPE=.137J

KE=ET-GPE KE=.221-.137 KE=.083J

V=KE=1/2mv2 .083=1/2(.050)v2 V=1.822J

D. GPE=(.050)(9.8)(0) GPE=0

KE=ET-GPE KE=.22-0 KE=.22J

ET=.22J

V=KE=1/2mv2 .22=1/2(.05)v2 V= 2.9m/s

Physics To Go
Page 244, February 4th, 2011 1. GPE=mgh GPE=(50kg)(9.8)(1) GPE=490J 2. The beginning, there is a lot of GPE and no KE, as they go down the hill, GPE decreases and KE increases. At the end, the GPE reaches 0 and KE begins to decrease as the brake is applied. 3. The force of gravity makes it impossible for someone to "hang" or float in midair, defying the force of gravity. 4. Someone who says it is possible to defy physics should be required to provide a counterclaim with observable and mathematical evidence. 5. Two ways to increase someone's jump height would be to strengthen their legs and become lighter so they can push off the ground stronger and with less resistance. 6a. W=fd W=(1N)(9.8)(1m) W=9.8J 6b. W=fd W=(1)(9.8)(10) W=98J 6c. W=fd W=(10)(9.8)(1) W=98J 6d. W=fd W=(.1)(9.8)(100) 6e. W=fd W=(100)(9.8)(.1) W=98J 7. mgh=mgd when D is lifted. 8. KE=GPE so therefore the answers are the same. 9. W=FD W=(50)(4 W=2150J 10. KE=1/2mv2 KE=1/2(62)(8.2)2 KE=2084.44J 11a. F=ma 30=5a a=6m/s 11b. W=fd W=(30)(18.75) W=562.5J 12a. W=fd 40000=3200d 12.5m=d 12b. F=ma 3200=1200a a=2.66m/s 13. W=KE KE=1/2mv2 KE=1/2(.15)(1600) W=-120J 14. W=KE W=1/2mv2 W=1/2(64)(225) W=7200 fd=7200 417d=7200 d=17.26m 15. 16. 17.
 * || Running || Full Bend || Peak || Landing ||
 * KE || max || some || some || max ||
 * GPE || none || none || max || decreasing ||
 * EPE || none || max || none || none ||
 * || Peak || Landing || Lowest ||
 * KE || max || some || lowest ||
 * GPE || max || some || lowest ||
 * EPE || none || none || max ||
 * || Top || Middle || Bottom ||
 * KE || lowest || increasing || max ||
 * GPE || max || decreasing || lowest ||
 * EPE || none || none || none ||