Bennett Mechanical Test Bennett Mechanical Work and Energy Questions and Answers 3

Question 1

A machine receives 800 J of input energy but delivers only 600 J of useful work. What is its efficiency?

Accepted Answer

75%

Answer

Efficiency = (useful output / input) × 100 = (600 / 800) × 100 = 75%.

Question 2

Which energy conversion takes place in a hydroelectric dam?

Accepted Answer

Gravitational potential to electrical

Answer

Water stored at height has gravitational potential energy that converts to kinetic energy, then to electrical energy via turbines.

Question 3

If the speed of a moving object is doubled, how does its kinetic energy change?

Accepted Answer

It quadruples

Answer

Since KE = ½mv², doubling velocity increases KE by a factor of 2² = 4 (quadruples).

Question 4

A 200 N force moves an object 3 m in the direction of the force. How much work is done?

Accepted Answer

600 J

Answer

W = F × d = 200 × 3 = 600 J.

Question 5

Horsepower (hp) is a unit used to measure which physical quantity?

Accepted Answer

Power

Answer

Horsepower is a unit of power, where 1 hp equals approximately 746 watts.

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