Question

An old building is being demolished by swinging a heavy metal ball from a crane. Suppose that such a 85kg ball swings from a 20-m-long wire at speed 10m/s as the wire passes the vertical orientation.

What tension force must the wire be able to withstand in order not to break?

Assume the ball stops after sinking 1.5 m into the wall. What was the average force that the ball exerted on the wall?

Answer 1

Ac = v^2/R
= 100/20 = 5 m/s^2
so
F = m g + 5 m = (9.81+5)m = 14.81 m
so F = 14.81*85 = 1258 Newtons

f = change in momentum / time
change in momentum = 85*10 = 850 kg m/s

time = distance/average speed
= 1.5/5 = .3 seconds
so
f = 850 kg m/s / .3 s = 2833 kg m/s^2
= 2833 Newtons