Solution Found!
A puck attached to a string moves in a circular path on a
Chapter 11, Problem 93GP(choose chapter or problem)
A puck attached to a string moves in a circular path on a frictionless surface, as shown in Figure 11–34. Initially, the speed of the puck is v and the radius of the circle is r. If the string passes through a hole in the surface, and is pulled downward until the radius of the circular path is r/2, (a) does the speed of the puck increase, decrease, or stay the same? (b) Calculate the final speed of the puck.
Questions & Answers
QUESTION:
A puck attached to a string moves in a circular path on a frictionless surface, as shown in Figure 11–34. Initially, the speed of the puck is v and the radius of the circle is r. If the string passes through a hole in the surface, and is pulled downward until the radius of the circular path is r/2, (a) does the speed of the puck increase, decrease, or stay the same? (b) Calculate the final speed of the puck.
ANSWER:
Solution 93 GP:
Step 1 of 2:-
a)
Here we have to find whether the speed of the puck increase decrease or remains the same.
The initial speed and radius were and
respectively.
When the radius decreases to , the moment of inertia decreases.
There are no external forces present, so the angular momentum must be conserved.
So,
As decreases,
must increase and therefore the speed
must increase.
Because,
So, the conservation of angular momentum compels the linear speed to increase.