Question

A .5kg ball on the end of a string is revolving uniformly in ahorizontal circle of radius 1m. The ball makes 2 revolustion in a second.
a) determine the linear (tangential) speed of the ball.
For this part of the question would I do this:
v=d/t
=1m/.5s
=2m/s
b)determine the ball's centripetal acceleration
a_c=v^2/r
=2m/s^2/1
=4m/s^2

c)determine the force a person must exert on the opposite end of the string.
F_c=mv^2/r
=.5kg(2m/s)^2/1
=2N

Is this correct? The only thing i'm not too sure about is part a). Thanks in advance for your help.

Answer 1

The distance around the circle is 2PI*radius, v= distance/time You have distance equal to radius.

The centripetal force is indeed v^2/r, your numbers are of course wrong.

part A messes up part b, c.