WTMA Energy, Work, and Power 3

Question 1

A ball rolling along a flat surface gradually slows down due to friction. Where does the kinetic energy go?

Accepted Answer

It converts to thermal energy (heat)

Answer

Friction converts kinetic energy into thermal energy, which is why surfaces warm slightly when objects slide across them.

Question 2

Which unit is commonly used to measure electrical power?

Accepted Answer

Watt

Answer

The watt (W) is the SI unit of power, including electrical power, equal to one joule per second.

Question 3

A 10 lb object is dropped from a height of 20 feet. Just before it hits the ground, approximately how much kinetic energy does it have (ignoring air resistance)?

Accepted Answer

200 ft-lb

Answer

The potential energy at the top (10 × 20 = 200 ft-lb) converts entirely to kinetic energy just before impact.

Question 4

A machine requires 1,000 watts of input power but delivers only 800 watts of useful output. What is its efficiency?

Accepted Answer

80%

Answer

Efficiency = (Useful Output / Input) × 100 = (800 / 1,000) × 100 = 80%.

Question 5

Which of the following is NOT a form of mechanical energy?

Accepted Answer

Chemical energy in a battery

Answer

Chemical energy in a battery is stored chemical energy, not mechanical energy; mechanical energy includes kinetic and potential forms.

WTMA - Wiesen Test of Mechanical Aptitude Practice Test

WTMA - Wiesen Test of Mechanical Aptitude Practice Test

WTMA Energy, Work, and Power 3