# Rotational dynamics

1. Jul 19, 2006

### vijay123

dear guys,
1)a solid cylinder of mass 20kg and radius 0.12m rotating with initial angular speed of 125ms-2 is placed lightly(ie without any translational push) on a horizontal table with co-efficient of kinectic energy of mu=0.15, between the cylinder and the table.
a)after how long does the cylinder start rolling?
b) what is the intial translational energy, rotational energy and the total energy of cylinder.

2)a cylinder of mass 10kg and radius 15cm is rolling perfectly on a plane of inclination 30degress. the coeffeicient of static friction is mu=0.25.
a)how much is the force of friction acting on the cylinder.

2. Jul 20, 2006

### Ukitake Jyuushirou

ur suppose to have done the work urself otherwise the physics expert in the forum wont help u

3. Jul 21, 2006

### vijay123

oh...ok fine..
here is how it goes...if you see the graph of static and kinetic friction, the line will slowly climb up until it reaches a certain point, known as static friction. so, in order to find the time, in which direction should the frictional torque be held?

4. Jul 21, 2006

### vijay123

i dont know about rolling, does it mean that the accelartaion is zero and the net torique is zero?

5. Jul 21, 2006