Work, Power, & Energy

Two football players are running toward each other. One football player has a mass of 105 kg and is running at 8.6 m/s. The other player has a mass of 90 kg and is running at -9.0 m/s. What is the momentum of the system after the football players collide?

• 93 kg m/s

• 810 kg m/s

• 903 kg m/s

Gymnasts often practice on foam floors, which increase the collision time when a gymnast falls. What effect does this have on collisions?

• The change in momentum needed to stop the gymnast is increased.

• The change in momentum needed to stop the gymnast is decreased.

• The force exerted by the floor on the gymnast decreases.

An object is moving north at a constant speed. A force of 5N begins to push the object east as a force of 5N begins to push it west. What will happen to the object?

• The object will slow down and stop.

• The object will accelerate.

• The object will continue moving north.

A car has a mass of 1200 kg. What is its acceleration when the engine exerts a force of 600N?

• 0.5 m/s squared

• 2 m/s squared

• 600 m/s squared

A probe is launched from Earth and lands on Mars. The gravitational acceleration on Mars is 3.7 m/s squared. Which statement best compares the mass and weight of the probe?

• The mass of the probe remains the same, but the weight of the probe increases.

• The mass of the probe remains the same, but the weight of the probe decreases.

• The mass of the probe increases, but the weight of the probe remains the same.

A skydiver is traveling at terminal velocity with her body parallel to the ground. She then changes her body position to feet first toward the ground. What happens to her motion?

• She will continue to fall at the same terminal velocity.

• She will slow down because the air resistance will increase.

• She will speed up because air resistance will decrease.

Which best compares the gravitational force and the strong force?

• Both are attractive and repulsive.

• Both are attractive only.

• Both are weaker than the electromagnetic force.

Which two forces act directly on objects that are unable to be viewed by the unaided eye?

• electromagnetic and strong

• gravitational and weak

• strong and weak

How are the weak and strong forces alike?

• They have very small ranges.

• They are attractive only.

• They have infinite ranges.

Which best contrasts the weak force and the electromagnetic force?

• The weak force acts within protons and neutrons, and the electromagnetic force has an infinite range.

• The weak force is attractive and repulsive, and the electromagnetic force is attractive only.

• The weak force is attractive only, and the electromagnetic force is attractive and repulsive.