Posted by **George** on Monday, September 20, 2010 at 2:09am.

In moving a 35.0 kg desk from one side of a classroom to the other, a professor finds that a horizontal force of 300 N is necessary to set the desk in motion, and a force of 185 N is necessary to keep it in motion at a constant speed.

(a) What is the coefficient of static friction between the desk and the floor?

(b) What is the coefficient of kinetic friction between the desk and the floor?

I know that F=ma, but how do you do this?

- Physics -
**drwls**, Monday, September 20, 2010 at 8:14am
You don't use F = ma. The desk is not accelerating. All that equation tells you is that the pusing force is equal to the opposiing friction force. The net force on the desk is zero.

The static coefficient of friction is 300N/(M g)

The kinetic coefficient of friction is

185/(M g)

Note that the denominator is the weight, not the mass.

Plug in for mass M and g (the acceleration of gravity) and crank away.

- Physics -
**George**, Tuesday, September 21, 2010 at 3:42am
Thanks!

## Answer this Question

## Related Questions

- Physics - In moving a 35.0 kg desk from one side of a classroom to the other, a ...
- PHYSICS - Example 2: a) A desk has a mass of 68.75 kilograms. If the coefficient...
- Physics - You set up a ramp on your desk at home. Marbles rolling down the ramp ...
- physics - Imagine yourself seated on a wheeled desk chair at your desk. Consider...
- math - Each student desk in a classroom has a rectangular desktop that measures ...
- Physics - a student pushes on a desk with a force of 75 N causing it to begin ...
- physics - A student pushes on a desk with a horizontal force of 125 N and moves ...
- English - What is in the classroom? 1. There is a blackboard in the classroom. 2...
- physics - A dockworker loading crates on a ship finds that a 17-kg crate, ...
- physics - A dockworker loading crates on a ship finds that a 19-kg crate, ...