QUESTION 1: A wheel of mass 0.49 kg and radius 44 cm is spinning with an angular
ID: 2298905 • Letter: Q
Question
QUESTION 1:
A wheel of mass 0.49 kg and radius 44 cm is spinning with an angular velocity of 19 rad/s. You then push your hand against the edge of the wheel, exerting a force F on the wheel as shown in the figure below. If the wheel comes to a stop after traveling 1/4 of a turn, what is F?
QUESTION 2:
A child of mass 52 kg jumps onto the edge of a merry-go-round of mass 140 kg and radius 1.7 m that is initially at rest as sketched in the figure below. While in the air (during her jump), the child's linear velocity in the direction tangent to the edge of the merry-go-round is 7 m/s. What is the angular velocity of the merry-go-round plus child after the child jumps onto the merry-go-round?
Explanation / Answer
2.
Use conservation of angular momentum.
mrv = 1/2 Mr^2 w + mr^2 w
2v = (M/m + 2) rw
w = 2(v/r) / (M/m + 2)
w = 2((7 m/s / 1.7 m) / (140 kg / 52 kg + 2)
w = 1.755 rad/s