Question

A 0.20-kg ball on a string is whirled on a vertical circle at a constant speed. When the ball is at the three o'clock position, the string tension is 16 N. Find the tensions in the string when the ball is at twelve o'clock and at the six o'clock positions.

* Physics - bobpursley, Tuesday, October 6, 2009 at 4:52pm

at three oclock, Tension= mv^2/r

then at 12 oclock,
tension= mv^2/r-mg
and at six...
tension= mv^2/r + mg

How do I solve for the r and the v?

Answer 1

YOu don't need it.

you know mv^2/r=16N

Answer 2

Just sub some numbers in to make it work. For example... tension/mass (16/.2)=80. So 80 is equal to rv^2. so make v=10 m/s and r =.8 m so everything will work out. It stays the same throughout so you can 'make up' the numbers