If a roofer falls from a height of 30 feet, how fast is he/she going when they h

Question

If a roofer falls from a height of 30 feet, how fast is he/she going when they hit the ground? it would he good practice to solve this problem using both Newton's second law and conservation of energy An object is launched by compressing a spring as shown in the sketch below. The object has a mass of 0.1 kg and the spring has a spring constant of 350 N/m. If the spring is compressed 10 cm before the object is released, how far does the object fly before impacting the ground? Note that theta = 30 degree.

Explanation / Answer

1.
h = 50 ft = 9.144 m
using newton's law:
A non balanced force due to acceleration due to gravity acts on it
a = 9.8 m/s^2
d = 9.144 m
vi = 0 m/s
usE:
vf^2 = vi^2 + 2*a*d
vf^2 = 0 + 2*9.8*9.144
vf=13.4 m/s
Answer: 13.4 m/s

solving using conservation of energy:
use:
potential energy at top = kinetic energy at bottom
m*g*h = 0.5*m*v^2
g*h = 0.5*v^2
9.8*9.144 = 0.5*v^2
v = 13.4 m/s
Answer: 13.4 m/s

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