Explanation:
a) The rope obeys Hooke's law, so:
F = k Δx
The elastic energy in the rope is:
EE = ½ k Δx²
Or, in terms of F:
EE = ½ F Δx
Use trigonometry to find the stretched length.
cos 20° = 35 / x
x = 37.25
So the displacement is:
Δx = 37.25 − 24
Δx = 13.25
The elastic energy per rope is:
EE = ½ (3.7×10⁴ N) (13.25 m)
EE = 245,000 J
There's two ropes, so the total energy is:
2EE = 490,000 J
Rounded to one significant figure, the elastic energy is 5×10⁵ J.
b) The elastic energy in the ropes is converted to gravitational energy.
EE = PE = mgh
5×10⁵ J = (1.2×10³ kg) (9.8 m/s²) h
h = 42 m
Rounded to one significant figure, the height is 40 m. So the claim is not justified.
