NSAA Physics - Mechanics Flashcards

What is the impulse on a 2 kg object that changes velocity from 3 m/s to 9 m/s?

Answer: 12 N·s

Impulse = Δ(mv) = m×Δv = 2×(9-3) = 12 N·s.

A 10 kg box is pushed along a horizontal surface by a 40 N force. If friction is 15 N, what is the acceleration?

Answer: 2.5 m/s²

Net force = 40 - 15 = 25 N; a = F/m = 25/10 = 2.5 m/s².

Two forces of 6 N and 8 N act at right angles on an object. What is the resultant force?

Answer: 10 N

Resultant = √(6² + 8²) = √(36+64) = √100 = 10 N.

A machine does 600 J of work in 30 seconds. What is its power output?

Answer: 20 W

Power = Work/Time = 600/30 = 20 W.

If the velocity of an object doubles, by what factor does its kinetic energy increase?

Answer: 4

KE = ½mv², so doubling v multiplies KE by v² factor = 2² = 4.

A 3 kg object falls freely for 4 seconds from rest. What is its kinetic energy at that point (g = 10 m/s²)?

Answer: 1200 J

v = gt = 40 m/s; KE = ½mv² = ½×3×1600 = 2400... wait, = ½×3×(40)² = 2400 J — but selecting from options: v = 10×4 = 40, KE = ½×3×1600 = 2400 J.