physics homework#8
vincesme
HWWeek5.docName ___________________________ Momentum HW Week 5 worksheet
1. A 30 cm spring with constant 70 N/m is compressed to 10 cm and placed between two carts. Cart A has mass
A
m
= 5kg andB
m
is unknown. Initially the system is at rest. After it is released it is observed that cart A has three times the velocity of cart B.a) What force must be exerted initially to keep the spring compressed?
b) What is the work done to compress the spring?
c) By considering conservation of momentum determine the mass
B
m
d) By considering conservation of energy find the velocities of the carts A and B after the spring is released.
2. A 0.30 kg ball is dropped onto a concrete driveway. The ball's velocity before impact is 4.5 m/s and after impact is 4.2 m/s. What is the change in the ball's momentum?
3. A 1.5 kg ball falls onto a floor. Just before it strikes the floor, its velocity is 12 m/s. The ball bounces up with a velocity of 10 m/s. Find the impulse on the ball.
4. A soccer player kicks a soccer ball initially at rest setting it in motion at a velocity of 30 m/s. If the ball has a mass of 0.50 kg and the time of contact is 0.025 s, what is the force exerted on the player’s foot?
5. A 1000 kg car traveling east at 20 m/s collides head-on with a 1500 kg car traveling west at 10 m/s. The cars stick together after the collision. What is their common velocity after the collision?
6. A 0.240 kg glider moving with a velocity of 0.600 m/s collides head-on with a 0.260 kg glider moving along the same line in the opposite direction with a velocity of 0.200 m/s. The collision is perfectly inelastic. What is the final velocity of the combined gliders?
7. A 15,000 kg railroad freight car is coasting at a speed of 2.0 m/s. It collides and couples with another car with a mass of 50,000 kg, which was initially not moving. What percentage of the initial kinetic energy of the system is preserved after collision?
8. A ballistic pendulum is a device used to measure the speed of a bullet. A bullet is fired at a block of wood hanging from two strings. The bullet embeds itself in the block and causes the combined block plus bullet system to swing up. If the bullet is fired at 530 m/s and its mass is 6.5 g, what is the speed of the block and the embedded bullet after collision? The mass of the block is 2.2 kg.
9. Using the same data from question 8, and the answer to question 8, how high will the pendulum’s block and the embedded bullet rise?
10. A bumper protects a car during a collision because it:
a) increases the time of impact
b) decreases the time of impact
c) increases the force of impact
d) increases kinetic energy transfer
