Hon Unit test Work, Power, Energy, Conservation of energy

During an emergency stop, a 1.5 × 10³-kilogram car lost a total of 4.69 × 10⁵ joules of kinetic energy. What was the speed of the car at the moment the brakes were applied?

• 10. m/s

• 14 m/s

• 20. m/s

• 25 m/s

A 6.8-kilogram block is sliding down a horizontal, frictionless surface at a constant speed of 8.4 meters per second. The kinetic energy of the block is approximately

• 20 J

• 41 J

• 120 J

• 240 J

A 45.0-kilogram boy is riding a 20.0-kilogram bicycle with a speed of 8.00 meters per second. What is the combined kinetic energy of the boy and the bicycle?

• 240. J

• 480. J

• 1920 J

• 2080 J

If the speed of a car is halved, the kinetic energy of the car is

• quadrupled

• quartered

• doubled

• halved

Which graph best represents the relationship between the kinetic energy, KE, and the velocity of an object accelerating in a straight line?

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A 1.0-kilogram rubber ball traveling east at 4.0 meters per second hits a wall and bounces back toward the west at 2.0 meters per second. Compared to the kinetic energy of the ball before it hits the wall, the kinetic energy of the ball after it bounces off the wall is

• one-fourth as great

• one-half as great

• the same

• four times as great

An object moving at a constant speed of 20 meters per second possesses 450 joules of kinetic energy. What is the object’s mass?

• 1.4 kg

• 2.25 kg

• 18 kg

• 36 kg

The diagram below shows block A, having mass m and speed 2v, and block B having mass 2m and speed v.

Compared to the kinetic energy of block A, the kinetic energy of block B is

• the same

• twice as great

• one-half as great

• four times as great

Two objects, 5 kg and 20 kg respectively, are released simultaneously from a height of 100. meters above the ground. After falling freely for 5.0 seconds, the objects will have different

• accelerations

• speeds

• kinetic energies

• displacements

As an object moves upward at a constant speed, its kinetic energy

• decreases

• increases

• remains the same