Exam 7: Energy

Two identical objects in outer space have a head-on collision and stick together.If,before the collision,one had been moving at 2 m/s and the other at 1 m/s,their combined speed after the collision would be

The power required to exert 1 N force,over a distance of 1 m in 1 second is

After rolling halfway down an incline,a marble's kinetic energy is

A machine puts out 100 Watts of power for every 1000 Watts put into it.The efficiency of the machine is

If an object is raised twice as high,its potential energy will be

A 1000-kg car and a 2000-kg car are hoisted the same distance.Raising the more massive car requires

Which requires the most amount of work by the brakes of a car?

A heavy and a light object released from the same height in a vacuum have equal

One end of a long,uniform log is raised to shoulder level.Another identical log is raised at its center to the same level.Raising the second log requires about

Two 5000-kg passenger cars roll without friction (one at 1 m/s,the other at 2 m/s)toward each other on a level track.They collide,couple,and roll away together with a combined momentum of

A bullet has more kinetic energy than the recoiling rifle from which it is fired is because the force on the bullet acts over a

A feather and a coin dropped in a vacuum fall with equal

An open freight car rolls friction free along a horizontal track in a pouring rain that falls vertically.As water accumulates in the car,the car's speed

A jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J.The efficiency of the jack system is

The total momentum of a flock of identical birds could be zero only if the birds are

A car moving at 50 km/hr skids 20 m with locked brakes.How far will the car skid with locked brakes if it were traveling at 150 km/hr?

A 2500-N pile-driver ram falls 10 m and drives a post 0.1 m into the ground.The average impact force on the ram is

Strictly speaking,more fuel is consumed by your car if an air conditioner,headlights,or even a radio is turned on.This statement is

Compared to the recoiling rifle,the bullet fired has

If several balls are thrown straight up with varying initial velocities,the quantity that will have the same value for each trial is the ball's