# Force and coefficient of friction problem

1. Oct 6, 2009

### demonelite123

A initially stationary block of mass "m" is on the floor. A force of magnitude 0.500mg is then applied at upward angle 20 degrees. What is the magnitude of the acceleration of the block across the floor if coefficient of static friction = 0.6 and coefficient of kinetic friction = 0.5?

i converted 0.5 mg into 5e-7 kg. so i drew a free body diagram and made the following equations: (F_N is the normal force)
F_N + 5e-7(sin 20) = 9.8m
5e-7(cos 20) - Fr = ma.

so i solved for F_N and substituted into second equation:
since Fr = F_N (coefficient of friction) but which coefficient of friction do i use in this scenario? also even if i do find which one to use, i can't eliminate m from the equation so how do i solve for a?

2. Oct 6, 2009

### rl.bhat

A force of magnitude 0.500*m*g is applied. Here m is the mass of the block.

3. Oct 6, 2009

### demonelite123

thank you! i can't believe i mistook mg for milligrams...