# What equation do i use to find the acceleration?

1. Sep 8, 2015

### rgold

1. The problem statement, all variables and given/known data
A person pushes horizontally with a force of 221 N on a 55.0 kg crate to move it to the right across a level floor. The coefficient of kinetic friction is 0.350. What is the magnitude of (a)the frictional force and (b) the crate's acceleration? Use g=9.81 m/s2.

2. Relevant equations
Fk=(Mk)(FN)

3. The attempt at a solution
i used the above equation to find the frictional force which was 188.65 N and i know the acceleration will be in m/s^2 but i dont know how to find the acceleration

2. Sep 8, 2015

### billy_joule

Can you draw a diagram with forces acting?
What direction does the frictional force act? What is the net force on the crate?

3. Sep 9, 2015

### HallsofIvy

Staff Emeritus
Since the mass of the crate is 55.0 kg and g= 9.81, the weight of the crate is 55.0*9.81= 539.55 Newtons. Multiply that by the given coefficient of friction, 0.350, to get the friction force, 188.8425, or to three significant figures, 189 Newtons. Subtract that from the applied force (assuming it is horizontal) to get the net force acting on the crate. Then use "F= ma" to find the acceleration.

4. Sep 9, 2015

thank you!