Question

A merry-go-round (pictured) is sitting in a playground. It is free to rotate, but is currently stationary. You can model it as a uniform disk of mass 200 kg and radius 110 cm (consider the metal poles to have a negligible mass compared to the merry-go-round). The poles near the edge are 97 cm from the center.

Someone hits one of the poles with a 9 kg sledgehammer moving at 19 m/s in a direction tangent to the edge of the merry-go-round. The hammer is not moving after it hits the merry-go-round.

How much energy is lost in this collision? (enter a positive number for the absolute value in Joules)

Answer 1

help plase

Answer 2

First, get all the variables:

m_1: The mass of the merry-go-round
m_2: The mass of the sledgehammer
v_1: The velocity of the merry-go-round before the collision
v_2: The velocity of the sledgehammer before the collision
v_1': The velocity of the merry-go-round after the collision
v_2': The velocity of the sledgehammer after the collision

Apply the conservation of momentum:

(m_1*v_1)+(m_2*v_2)=(m_1*v_1')+(m_2*v_2')

You know everything except for v_1', so you can solve the above equation for v_1'. Then look at the difference in kinetic energy before and after the collision:

((0.5*m_1*v_1^2)+(0.5*m_2*v_2^2))-((0.5*m_1*v_1'^2)+(0.5*m_2*v_2'^2))

The above is your answer.

Answer 3

so the radius is not important???
and we'll have to consider v_1=0 and v_2'=0

v_1'=mhammer*vhammer/Mmerry???!!!!