PHYSICS FINAL

Two ice dancers are at rest on the ice, facing each other with their hands together. They push off on each other in order to set each other in motion. The subsequent momentum change (magnitude only) of the two skaters will be ____.

the same for each skater

Two pop cans are at rest on a stand. A firecracker is placed between the cans and lit. The firecracker explodes and exerts equal and opposite forces on the two cans. Assuming the system of two cans to be isolated, the post-explosion momentum of the system ____.

0

A 1.5-kg cannon is mounted on top of a 2.0-kg cart and loaded with a 52.7-gram ball. The cannon, cart, and ball are moving forward with a speed of 1.27 m/s. The cannon is ignited and launches a 52.7-gram ball forward with a speed of 75 m/s. Determine the post-explosion velocity of the cannon and cart.

0.160 m/s

If a ball is projected upward from the ground with ten units of momentum, what is the momentum of recoil of the Earth? ____________ Do we feel this? Explain

10 units of momentum. This is not felt by Earth's occupants. Since the mass of the Earth is extremely large, the recoil velocity of the Earth is extremely small and therefore not felt.

A 62.1-kg male ice skater is facing a 42.8-kg female ice skater. They are at rest on the ice. They push off each other and move in opposite directions. The female skater moves backwards with a speed of 3.11 m/s. Determine the post-impulse speed of the male skater.

2.14 m/s

Ben Travlun carries a 200-N suitcase up three flights of stairs (a height of 10.0 m) and then pushes it with a horizontal force of 50.0 N at a constant speed of 0.5 m/s for a horizontal distance of 35.0 meters. How much work does Ben do on his suitcase during this entire motion?

3750 J

Calculate the work done by a 2.0-N force (directed at a 30° angle to the vertical) to move a 500 gram box a horizontal distance of 400 cm across a rough floor at a constant speed of 0.5 m/s. (HINT: Be cautious with the units.)

4.0 J

A car possesses 20 000 units of momentum. What would be the car's new momentum if ... its mass was doubled (by adding more passengers and a greater load)

40 000 units (doubling the mass = double the momentum)

A car possesses 20 000 units of momentum. What would be the car's new momentum if ...its velocity was doubled.

40 000 units (doubling velocity=doubling momentum)

How much work is done by an applied force to lift a 15-Newton block 3.0 meters vertically at a constant speed?

45 Joules

A car possesses 20 000 units of momentum. What would be the car's new momentum if ... its velocity was tripled.

60 000 units (tripling velocity=triple the momentum)

A student with a mass of 80.0 kg runs up three flights of stairs in 12.0 sec. The student has gone a vertical distance of 8.0 m. Determine the amount of work done by the student to elevate his body to this height. Assume that his speed is constant.

6272 Joules

A car possesses 20 000 units of momentum. What would be the car's new momentum if ...both its velocity was doubled and its mass was doubled.

80 000 units (4x)

A large truck and a Volkswagen have a head-on collision. Which vehicle experiences the greatest acceleration?

Acceleration is greatest for the Volkswagon. While the two vehicles experience the same force, the acceleration is greatest for the Volkswagon due to its smaller mass.

Miles Tugo and Ben Travlun are riding in a bus at highway speed on a nice summer day when an unlucky bug splatters onto the windshield. Miles and Ben begin discussing the physics of the situation. Miles suggests that the momentum change of the bug is much greater than that of the bus. After all, argues Miles, there was no noticeable change in the speed of the bus compared to the obvious change in the speed of the bug. Ben disagrees entirely, arguing that that both bug and bus encounter the same force, momentum change, and impulse. Who do you agree with?

Ben Travlun is correct.

. A 0.50-kg cart (#1) is pulled with a 1.0-N force for 1 second; another 0.50 kg cart (#2) is pulled with a 2.0 N-force for 0.50 seconds. Which cart (#1 or #2) has the greatest acceleration? Explain.

Cart #2 has the greatest acceleration. acceleration depends on force and mass.

While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?

Each force is the same size.

Jennifer, who has a mass of 50.0 kg, is riding at 35.0 m/s in her red sports car when she must suddenly slam on the brakes to avoid hitting a deer crossing the road. She strikes the air bag, that brings her body to a stop in 0.500 s. What average force does the seat belt exert on her?

F = (mass * velocity change)/time; 3500 N

A hockey player applies an average force of 80.0 N to a 0.25 kg hockey puck for a time of 0.10 seconds. Determine the impulse experienced by the hockey puck.

Impulse = F*t = 80 N * 0.1 s, 8 N*s

Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3 m/s.

KE = 1.05 x105 Joules

If a 5-kg bowling ball is projected upward with a velocity of 2.0 m/s, then what is the recoil velocity of the Earth (mass = 6.0 x 1024 kg).

Since the ball has an upward momentum of 10 kg*m/s, the Earth must have a downward momentum of 10 kg*m/s. To find the velocity of the Earth, use the momentum equation, p = m*v. This equation rearranges to v=p/m. v = (10 kg*m/s)/(6*1024 kg) v = 1.67*10-24 m/s (downward)

A 0.50-kg cart (#1) is pulled with a 1.0-N force for 1 second; another 0.50 kg cart (#2) is pulled with a 2.0 N-force for 0.50 seconds. Which cart (#1 or #2) has the greatest impulse? Explain.

The impulse is the same for each cart. Impulse is force*time

A 0.50-kg cart (#1) is pulled with a 1.0-N force for 1 second; another 0.50 kg cart (#2) is pulled with a 2.0 N-force for 0.50 seconds. Which cart (#1 or #2) has the greatest change in momentum? Explain.

The momentum change is the same for each cart. Momentum change equals the impulse

If a force of 14.7 N is used to drag the loaded cart (from previous question) along the incline for a distance of 0.90 meters, then how much work is done on the loaded cart?

W = 13.2 J

momentum change is equal to

impulse

For years, space travel was believed to be impossible because there was nothing that rockets could push off of in space in order to provide the propulsion necessary to accelerate. This inability of a rocket to provide propulsion in space is because ...

nonsense! Rockets do accelerate in space and have been able to do so for a long time.

Determine the momentum of a ... a. 60-kg halfback moving eastward at 9 m/s. b. 1000-kg car moving northward at 20 m/s. c. 40-kg freshman moving southward at 2 m/s.

p = m*v 540 kg•m/s, east, 80 kg•m/s, south, 20 000 kg•m/s, north,

A large truck and a Volkswagen have a head-on collision. Which vehicle experiences the greatest force of impact?

same

A large truck and a Volkswagen have a head-on collision. Which vehicle experiences the greatest impulse?

same

A large truck and a Volkswagen have a head-on collision. Which vehicle experiences the greatest momentum change?

same

Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowder explosion creates hot gases that expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. The acceleration of the recoiling rifle is ...

smaller than the acceleration of the bullet.