Coefficient of friction (between road and wheels of accelerating truck)

[pmp]

Homework Statement

What is the coefficient of friction between the road and the wheels of a 1400kg truck accelerating at 2 m/s/s if the force applied by the engine to the wheels is 4000N.

Homework Equations

F_n = m * g
F_f = mu * F_n

The Attempt at a Solution

I do not know how to resolve this as I don't know F_f or mu (i.e. two variables)
Any asisstance (not answer) would be appreciated.

 

[rock.freak667]

First draw a free body diagram.

Then find the resultant force in the horizontal (x) direction.

Newton's 2^nd Law states that ∑F_x= ma

 

[pmp]

thanks rock.freak667,
I have found the answer it was on a website called http://www.physics247.com/physics-homework-help/friction-and-weight.php" the answer was 0.09 as is shown here:

mu = F_f/F_n
F_f = (ma) - F_engine
mu = ((ma) - F_engine)/-(mg)
mu = ((1400 * 2) - 4000)/-(1400 * 9.81)
mu = (2800 - 4000)/-13734
mu = -1200/-13734
mu = 0.085...
mu = 0.09

 

[rock.freak667]

Once you understand the thinking process, as that will allow you do similar problems or slightly more complex ones.