Enter
F-20 N
F-2.AN
shift
0.Sis
Name:
Section:
Question 4. [25 points]
F-20N
A In each case at right, a ball bearing that is
spinning freely in a counterclockwise direction is
subjected to a stream of air that acts to slow the
bearing down. Due to the air stream, each bearing
will eventually stop rotating counterclockwise
F1.8N
F-25N
F-24 N
and start rotating clockwise. The angular speed of
each beaning when the stream is first applied, and
the force that each stream of air exerts on the
m), -0.5/
bearing are given in each figure. All of the
bearings are identical, and the nozzle directing the air stream is in the same position in each case. Assume the force due to the
air stream acts on the rim of the bearing.
i Rank these situations on the basis of the magnitude of the angular acceleration of the bearings at an instant while the
bearings are slowing down. Explain your reasoning.
,-
0.6/s
ii. Suppose the radius of the bearing is 0.08 meters and the mass of the bearings is 0.4 kg,
(a) Determine the time it would take for the bearing in situation A to come to rest. Show all work.
Angular velocity
Angular acceleration
Net Torque
(b) Consider the entire motion of the
bearing in situation A (rotating
counter clockwise and slowing down,
coming to rest for an instant, and then
rotating clockwise and speeding up.
Sketch graphs for the angular
velocity, the angular acceleration, and
the net Torque, as a function of time
for the entire motion. The time at
which the bearing switches direction
is indicated in each graph with a hatch mark.