Chapter 6: Work, Energy and Power

• W = Fs cosθ
• KE = ⅔mv²
• PE = mgh
• P = W/t = Fv

Q1. Find the work done by a force of 10 N at 60° to the displacement of 5 m.

Solution

W = Fs cosθ = 10 × 5 × cos60° = 50 × 0.5 = 25 J

Q2. A 2 kg ball is dropped from height 10 m. Find its velocity just before hitting the ground.

Solution

v² = u² + 2gh = 0 + 2(10)(10) = 200
v = √200 = 10√2 ≈ 14.14 m/s