AP Physics Physics: Classical Mechanics & Kinematics 5

Question 1

A ball is thrown horizontally at 10 m/s from a cliff. After 2 s, what is the ball's vertical velocity component? (g = 10 m/s²)

Accepted Answer

20 m/s downward

Answer

Vertical velocity = gt = 10 × 2 = 20 m/s downward (horizontal launch means initial vertical velocity is zero).

Question 2

Which of the following is an example of a non-inertial reference frame?

Accepted Answer

A car accelerating from a stoplight

Answer

An accelerating car is a non-inertial frame because Newton's first law does not hold without introducing pseudo-forces.

Question 3

A block of mass 4 kg sits on a surface with μs = 0.5. What is the minimum horizontal force needed to start the block moving? (g = 10 m/s²)

Accepted Answer

20 N

Answer

Maximum static friction = μs × mg = 0.5 × 4 × 10 = 20 N; the applied force must exceed this to start motion.

Question 4

A sprinter starting from rest reaches 9 m/s in 3 s. What is the sprinter's average acceleration?

Accepted Answer

3 m/s²

Answer

Average acceleration = Δv/Δt = (9 − 0)/3 = 3 m/s².

Question 5

Two vectors A = 3 m East and B = 4 m North are added. What is the direction of the resultant vector relative to East?

Accepted Answer

53° North of East

Answer

θ = arctan(4/3) ≈ 53° North of East; the larger northward component makes the angle closer to North.

AP Practice Test