Answer:
-360 kJ
Explanation:
Given:
m = 800 kg
v₀ = 30 m/s
v = 0 m/s
Δx = 75 m
Find: W
We can solve this using either forces or energy.
To use forces, first find the acceleration.
v² = v₀² + 2aΔx
(0 m/s)² = (30 m/s)² + 2a (75 m)
a = -6 m/s²
Then apply Newton's second law:
∑F = ma
F = (800 kg) (-6 m/s²)
F = -4800 N
Work is force times distance:
W = FΔx
W = (-4800 N) (75 m)
W = -360,000 J
W = -360 kJ
If you want to use energy instead:
work = change in energy
W = ΔKE
W = ½mv² − ½mv₀²
W = ½ (800 kg) (0 m/s)² − ½ (800 kg) (30 m/s)²
W = -360,000 J
W = -360 kJ
