7-51. A boy is playing with a rope tied to a tree near his favourite swimming hole (See the Figure). Initially the boy is stationary and the rope (of length 3.7 m) makes an angle of 48o with the vertical. He then lifts his feet slightly and starts to swing freely. If air resistance is neglected, use conservation of energy to determine:
(a) his speed at the bottom of the swing
(b) the minimum height, relative to his initial position, to which he can swing.
 
 
 
 
 
 
 
 
 
 
 


ACCUMULATED SOLUTION
 
 
 
 
 
 
 
 
 
 

Correct.
In fact all three choices are valid. We will choose it at point 2 in the figure at the bottom of the swing.

At point 2, a logical choice for the potential energy is:
(A)   0
(B)   mgh
(C)   (1/2)mv2