Physics Mechanics 3

Question 1

A 2 kg object moving at 6 m/s has its velocity reduced to 2 m/s by friction. How much kinetic energy was lost?

Accepted Answer

32 J

Answer

ΔKE = ½(2)(6²) − ½(2)(2²) = 36 − 4 = 32 J.

Question 2

According to Newton's Third Law, when a horse pulls a cart forward, the cart pulls the horse:

Accepted Answer

Backward with an equal and opposite force

Answer

Newton's Third Law states that every action force has an equal and opposite reaction force, so the cart pulls the horse backward with the same magnitude.

Question 3

A spring with a spring constant of 200 N/m is compressed by 0.1 m. How much elastic potential energy is stored?

Accepted Answer

1 J

Answer

Elastic PE = ½kx² = ½ × 200 × (0.1)² = 1 J.

Question 4

Which condition must be true for an object to be in static equilibrium?

Accepted Answer

Net force is zero and net torque is zero

Answer

Static equilibrium requires both the net force and the net torque on the object to equal zero.

Question 5

An elevator accelerates upward at 2 m/s². What does a 70 kg person feel as their apparent weight? (g = 9.8 m/s²)

Accepted Answer

826 N

Answer

Apparent weight = m(g + a) = 70 × (9.8 + 2) = 70 × 11.8 = 826 N.

Physics Practice Test

Physics Practice Test

Physics Mechanics 3