Physics: Classical Mechanics & Kinematics Flashcards

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)

Answer: 20 m/s downward

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

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

Answer: A car accelerating from a stoplight

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

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)

Answer: 20 N

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

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

Answer: 3 m/s²

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

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

Answer: 53° North of East

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

Which scenario correctly illustrates the concept of relative velocity?

Answer: A passenger walks forward at 2 m/s on a train moving at 10 m/s; a ground observer sees them move at 12 m/s

Velocities add when moving in the same direction: v_ground = v_train + v_passenger = 10 + 2 = 12 m/s.

A car travels 60 km north, then 80 km east. What is the magnitude of its displacement from the starting point?

Answer: 100 km

Displacement = √(60² + 80²) = √(3600 + 6400) = √10000 = 100 km.