# Homework Help: Center of Mass Prob

1. Mar 21, 2004

### SsUeSbIaEs

A girl throws a stick with a length of 0:25 m
and a mass of 0.53 kg into the air in such a
way that the center of mass rises vertically.
At the moment it leaves her hand, the stick
is horizontal and the speed of the end of the
stick nearest to her is zero. When the center
of mass of the stick reaches its highest point,
the stick is horizontal, and it has made 33
complete revolutions. Assume that the stick's
cross sectional area and mass is uniform.
The acceleration of gravity is 9.8 m/s^2 (speed of stick end
is zero when it leaves her hand)
How long did it take for the center of mass
to reach its highest point? Answer in units of
s.

2. Mar 22, 2004

### Staff: Mentor

Realize that you can express the angular speed &omega; of the stick in terms of the time it takes to get to the top, which is what you are trying to find. Also realize that at the moment the stick is released, the speed of the center of mass is related to the angular speed of the stick: V=&omega;R. Then apply what you (I hope) know about accelerated motion.

3. Mar 22, 2004

### SsUeSbIaEs

Thanks that helped a lot!