Physics - Review (Units 1 - 4)

A person is standing on a bathroom scale in an elevator car. If the scale reads a value greater than the weight of the person at rest, the elevator car could be moving

• downward at constant speed

• upward at constant speed

• downward at increasing speed

• upward at increasing speed

The force required to start an object sliding across a uniform horizontal surface is larger than the force required to keep the object sliding at a constant velocity. The magnitudes of the required forces are different in these situations because the force of kinetic friction

• is greater than the force of static friction

• is less than the force of static friction

• increases as the speed of the object relative to the surface increases

• decreases as the speed of the object relative to the surface increases

A 50.-kilogram student threw a 0.40-kilogram ball with a speed of 20. meters per second. What was the magnitude of the impulse that the student exerted on the ball?

• 8.0 N•s

• 78 N•s

• 4.0 × 10² N•s

• 1.0 × 10³ N•s

A box is pushed toward the right across a classroom floor. The force of friction on the box is directed toward the

• left

• right

• ceiling

• floor

A 40.-kilogram mass is moving across a horizontal surface at 5.0 meters per second. What is the magnitude of the net force required to bring the mass to a stop in 8.0 seconds?

• 1.0 N

• 5.0 N

• 25 N

• 40. N

What is the speed of a 1.0 × 10³-kilogram car that has a momentum of 2.0 × 10⁴ kilogram•meters per second east?

• 5.0 × 10^–2 m/s

• 2.0 × 10¹ m/s

• 1.0 × 10⁴ m/s

• 2.0 × 10⁷ m/s

A man standing on a scale in an elevator notices that the scale reads 30 newtons greater than his normal weight. Which type of movement of the elevator could cause this greater-than-normal reading?

• accelerating upward

• accelerating downward

• moving upward at constant speed

• moving downward at constant speed

A 60-kilogram skydiver is falling at a constant speed near the surface of Earth. The magnitude of the force of air friction acting on the skydiver is approximately

• 0 N

• 6 N

• 60 N

• 600 N

When a 12-newton horizontal force is applied to a box on a horizontal tabletop, the box remains at rest. The force of static friction acting on the box is

• 0 N

• between 0 N and 12 N

• 12 N

• greater than 12 N

Ball A of mass 5.0 kilograms moving at 20. meters per second collides with ball B of unknown mass moving at 10. meters per second in the same direction. After the collision, ball A moves at 10. meters per second and ball B at 15 meters per second, both still in the same direction. What is the mass of ball B?

• 6.0 kg

• 2.0 kg

• 10. kg

• 12 kg