Explanation:
(a) You can solve this using kinematics or energy.
Using kinematics:
a = F/m = 90 N / 4 kg = 22.5 m/s²
v₀ = 0 m/s
Δx = 5 m
Find: v
v² = v₀² + 2aΔx
v² = (0 m/s)² + 2 (22.5 m/s²) (5 m)
v = 15 m/s
Using energy:
W = ΔKE
Fd = ½ mv²
(90 N) (5 m) = ½ (4 kg) v²
v = 15 m/s
(b) ΔU = mg Δh
ΔU = (4 kg) (9.8 m/s) (12 m sin 40° − 15 m)
ΔU = -290 J
W = ΔU = -290 J
