6-23.A child has
tied a piece of wood of mass 0.47 kg to a string and is swinging it in
a vertical circle of radius 83 cm. At the top of the circle:
(a) draw a free
body diagram for the wood,
(b) determine the
magnitude of the tension in the string, if the speed of the wood is 3.7
m/s.
ACCUMULATED SOLUTION
Correct!
Both the weight
and the tension in the string act toward the centre when the block is
in
this position
(Note that this
is not the case anywhere else. For example, at the bottom of the circle
the tension is still toward the centre (up), but the weight acts down.)
The correct form of Newton's second law in this case is:
(A) mg + T = m(v2/r)
(B) mg - T = m(v2/r)
(C) T - mg = m(v2/r)