How Do You Calculate Acceleration with Friction Involved?

[halo9909]

Homework Statement

A 219-kg crate is pushed horizontally with a force of 710 N. If the coefficient of friction is 0.20, calculate the acceleration of the crate.

m=219kg
force of friction= 219kg *.2 =43.8N?

Homework Equations

f=ma?

The Attempt at a Solution

I am not sure at all how to calculate the acceleration and what to use as the "F" to calcuate it

 

[aimslin22]

friction is normal force*coefficient of friction

thus the force of friction would by 219*gravity*.2

The equation, F=ma, is right.

But friction always points in the opposite direction so it would set up like this:

Force(710) - friction = ma

then solve for a!

Hope this helps.

 

[halo9909]

yeah that does help
since I didnt realize you had to subtract the 710 with the Ff

so 710-429.24=280.76N
280.76N/219=1.282
a=1.282m/s^2

 

[aimslin22]

yup, I didn't do the actually calculations, but it looks right.
An easy way to remember this is :

winner force - loser force = ma

And free-body diagramming it helps too