P And J Review TEACHER ANSWER KEY February 10, 2003 2 1. The diagram shows two carts on a horizontal, frictionless surface being pushed apart when a compressed spring attached to one of the carts is released. Cart A has a mass of 3.0 Ho- grams and cart B has a mass of 5.0 kilograms. The speed of cart A is 0.33 meter/second after the spring is released. If the carts are initially at rest, what is the approximate speed of cart B after the spring is released? 1. 0. 12 m/s 3. 0.33 m/s 2. 0.20 m/s 4. 0.55 m/s No Explanation Available. 2 2. The mass of a space shuttle is approximately 2.0 x10 6 kilograms. During liftoff, the net force on the shuttle is 1.0 x10 7 newtons directed upward. What is the speed of the shuttle 10. seconds after lift-off? [Neglect air resistance and the mass change of the shuttle.] 1. 5.0 x10 0 m/s 3. 5.0 x 10 2 m/s 2. 5.0 x10 1 m/s 4. 5.0 x 10 3 m/s No Explanation Available. 1 3. A 50.-kilogram woman wearing a seat belt is traveling in a car that is moving with a velocity of + 10. meters per second. In an emergency, the car is brought to a stop in 0.50 second. What force does the seat belt exert on the woman so that she remains in her 1. -1.0 x 10 3 N 3. -5.0 x 10 1 N 2. -5.0 x 10 2 N 4. -2.5 x 10 1 N
No Explanation Available. 3 4. A bullet traveling at 5.0 x 10 2 meters per second is brought to rest by an impulse of 50. newton-seconds. What is the mass of the bullet? 1. 2.5 x 10 4 kg 3. 1.0 x 10-1 kg 2. 1.0 x 10 1 kg 4. 1.0 x 10-2 kg No Explanation Available. 2 5. A 2.0 X 10 3 -kilogram car collides with a tree and is brought to rest in 0.50 second by an average force of 6.0 X 10 4 newtons. What is the magnitude of the impulse on the car during this 0.50-second interval? 1. (1) 3. (3) 2. (2) 4. (4) 3 6. A student drops two eggs of equal mass simultaneously from the same height. Egg A lands on the tile floor and breaks. Egg B lands intact, without
bouncing, on a foam pad lying on the floor. Compared to the magnitude of the impulse on egg A as it lands, the magnitude of the impulse on egg B as it lands is 1. less 3. the same 2. greater No Explanation Available. 2 7. A 1,000-kilogram car traveling with a velocity of +20. meters/second decelerates uniformly at -5.0 meters/second squared until it comes to rest. What is the magnitude of the impulse applied to the car to bring it to rest? 1. 1.0 X 10 4 N*s 3. 3.9 x 10 4 N*s 2. 2.0 x 10 4 N*s 4. 4.3 x 10 4 N*s No Explanation Available. 1 8. What is the momentum of a 1.5 X 10 3 -kilogram car as it travels at 30. meters per second due east for 60. seconds? 1. (1) 3. (3) 2. (2) 4. (4)
3 9. If a net force of 10 newtons acts on a 6.0 kilogram mass for 8.0 seconds, total change of momentum of the mass is 1. 48 kg * meters/seconds 3. 80 kg * meters/seconds 2. 60 kg * meters/seconds 4. 480 kg * meters/seconds No Explanation Available. 3 10. What is the momentum of a 1,200-kilogram car traveling at 15 meters per second due east? 1. (1) 3. (3) 2. (2) 4. (4)
3 11. A 0.050-kilogram bullet is fired from a 4.0-kilogram rifle that is initially at rest. If the bullet leaves the rifle with momentum having a magnitude of 20. kilogram meters per second, the rifle will recoil with a momentum having a magnitude of 1. (1) 3. (3) 2. (2) 4. (4) 3 12. The magnitude of the momentum of an object is...(see image) If the velocity of the object is doubled, select from the choices shown the magnitude of the momentum of the object.
1. (1) 3. (3) 2. (2) 4. (4) 2 13. The accompanying diagram shows two carts that were initially at rest on a horizontal, frictionless surface being pushed apart when a compressed spring attached to one of the carts is released. Cart A has a mass of 3.0 kilograms and cart B has a mass of 5.0 kilograms. If the speed of cart A is 0.33 meter per second after the spring is released, what is the approximate speed of cart B after the spring is released? 1. 0.12 m/s 3. 0.33 m/s 2. 0.20 m/s 4. 0.55 m/s 1 14. Base your answer on the information below and on the diagram shown. The diagram shows a compressed spring between two carts initially at rest on a horizontal frictionless surface. Cart A has a mass of 2 kilograms and cart B has
a mass of 1 kilogram. A string holds the carts together. What occurs when the string is cut and the carts move apart? 1. The magnitude of the acceleration of cart A is one-half the magnitude of the acceleration of cart B. 2. The length of time that the force acts on cart A is twice the length of time the force acts on cart B. 3. The magnitude of the force exerted on cart A is one-half the magnitude of the force exerted on cart B. 4. The magnitude of the impulse applied to cart A is twice the magnitude of the impulse applied to cart B. 1 15. Base your answer on the information below and on the diagram shown. The diagram shows a compressed spring between two carts initially at rest on a horizontal frictionless surface. Cart A has a mass of 2 kilograms and cart B has a mass of 1 kilogram. A string holds the carts together. After the string is cut and the two carts move apart, the magnitude of which quantity is the same for both carts? 1. momentum 3. inertia
2. velocity 4. kinetic energy 4 16. Which is an acceptable unit for impulse? 1. (1) 3. (3) 2. (2) 4. (4) 3 17. During a collision, an 84-kilogram driver of a car moving at 24 meters per second is brought to rest by an inflating air bag in 1.2 seconds. The magnitude of the force exerted on the driver by the air bag is approximately 1. 7.0 x 10 1 N 3. 1.7 x 10 3 N 2. 8.2 x 10 2 N 4. 2.0 x 10 3 N
2 18. The accompanying diagram shows a 4.0-kilogram cart moving to the right and a 6.0-kilogram cart moving to the left on a horizontal frictionless surface. When the two carts collide they lock together. The magnitude of the total momentum of the two-cart system after the collision is 1. 1 3. 3 2. 2 4. 4
3 19. The accompanying diagram shows two carts initially at rest on a horizontal frictionless surface being pushed apart when a compressed spring attached to one of the carts is released. If the 1.0-kilogram cart moves to the left with a speed of 6.0 meters per second, then the 2.0-kilogram cart moves to the right with a speed of 1. 6.0 m/s 3. 3.0 m/s 2. 2.0 m/s 4. 12 m/s 2
20. A bullet traveling at 5.0 X 10 2 meters per second is brought to rest by an impulse of 50. newton seconds. What is the mass of the bullet? 1. 1.0 X 10-2 kg 3. 1.0 X 10 1 kg 2. 1.0 X 10-1 kg 4. 2.5 X 10 4 kg 21. A 4.0 x 10 3 kg truck runs crashes into a 5.0 x 10 2 kg parked car and the two vehicles move together with a velocity of 7.0 m/s. a) What type of collision is this? Inelastic b) What was the initial velocity of the truck? mava mbvb ( ma mb ) v' (4.0 x 10 3 kg )(m a ) + (5.0 x 10 2 kg)(0 m/s) = (4.0 x 10 3 kg+5.0 x 10 2 kg)(7.0 m/s) (4.0 x 10 3 kg )(m a ) = (4.5 x 10 3 kg)(7.0 m/s) (4.0 x 10 3 kg )(m a ) = (31500 kg m/s) 31500kgm / s m a 4.0 x 10 3 kg m a = 7.9 m/s 22. Two bumper cars are heading toward each other. Car A is has a mass of 45 kg heading east with a velocity of 20. m/s and car B heads west with a velocity of 14 m/s. After the collision, car A moves west with a velocity of 7.5m/s. and car B moves east with a velocity of 12 m/s. a) What type of collision is this? Elastic b) What is the mass of car B? m a = 45 kg v a = +20m/s (east) v a = -7.5 m/s (west) m b =? v b = -14 m/s (west) v b = +12 m/s (east) mava mbvb mava ' mbvb' (45 kg)(20 m/s) + m b (-14 m/s)=(45 kg)(-7.5 m/s)+ m b (12 m/s) (900 kg m/s)+ m b (-14 m/s)=-337.5 kg m/s+ m b (12 m/s) +337.5 kg m/s +337.5 kg m/s 1237.5 kg m/s +14m/s(m b ) +14m/s(m b )
1237.5 kg m/s = 26m/s(m b ) 1237.5kgm / s 26m / s m b m b =48 kg c) What is the momentum of the system before the collision? P before = P a +P b P before = 1237.5kg m/s + (48kg)(-14m/s) P before = 570 kg m/s