Coefficient of friction problem

[kranav]

Homework Statement

a body of mass 10 kg lies on a rough horizontal surface with an acceleration of 5 m/s and when the horizontal force us doubled , it gets an acceleration of 18 m/s^2. Then the coefficient of friction between the body and the horizontal surface is:

A) 0.2 B) 0.8 C) 0.4 D) 0.6

Homework Equations

fnet = f - umg = ma1 1st case
Fnet = F - umg = ma2 2nd case

The Attempt at a Solution

I tried to solve it but u comes out to be zero.

 

[Doc Al]

fnet = f - umg = ma1 1st case
Fnet = F - umg = ma2 2nd case

This looks good. (How do f and F relate?)

The Attempt at a Solution

I tried to solve it but u comes out to be zero.

Try it one more time.

 

[kranav]

This looks good. (How do f and F relate?)


Try it one more time.

thanks! got the answer!