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61.
CONCEPT QUESTIONS
a.
Since the speed and mass are constant and the radius
is fixed, the centripetal force is the same at each point on the circle.
b.
When the ball is at the three o’clock position, the force of gravity, acting
downward, is perpendicular to the string and cannot contribute to the centripetal
force. (See Figure 5.21, point 2 for a similar situation.) At this point, only the tension
of
T
= 16 N contributes to the centripetal force. Considering that the centripetal force
is the same everywhere, we can conclude that it has a value of 16 N everywhere.
c.
At the twelve o’clock position the tension
T
and the force of gravity
mg
both act
downward (the negative direction) toward the center of the circle, with the result that
the centripetal force at this point is –
T
–
mg
. (See Figure 5.21, point 3.) The
magnitude of the centripetal force here, then, is
T
+
mg
. At the six o’clock position
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This note was uploaded on 01/29/2010 for the course CALC 01:640:135 taught by Professor Soffer during the Spring '08 term at Rutgers.
 Spring '08
 SOFFER

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