Tangential Forces

1. Nov 4, 2007

Heat

1. The problem statement, all variables and given/known data

The carbide tips of the cutting teeth of a circular saw are 8.6cm from the axis of rotation.

The no-load speed of the saw, when it is not cutting anything, is 4800 rev/min. Why is its no-load power output negligible?

While the saw is cutting lumber, its angular speed slows to 2400rev/min and the power output is 1.9hp. What is the tangential force that the wood exerts on the carbide tips?

3. The attempt at a solution

Would part a be that it's like that because it's not producing any work, there is no friction or any force acting/slowing down the rev/min.?

How do I start part b?

Before: 4800 rev/min 0hp
After 2400 rev/min 1.9hp

How would I calculate the tangential forces.?

2. Nov 4, 2007

Staff: Mentor

Well, at constant speed, it is accelerating, i.e. there is not angular acceleration.

See - http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html - for equations of rotational motion.

See the relationship between torque, angular velocity and power. For relationship between applied force on moment arm and torque, see -

http://hyperphysics.phy-astr.gsu.edu/hbase/torq2.html#tc