An object with a mass of 7 kg is on a surface with a kinetic friction coefficient of  8 . How much force is necessary to accelerate the object horizontally at  31 m/s^2?

Dec 30, 2015

I found $765.8 N$ (but check my maths!). Ciao.

Explanation:

Have a look:

So we get that:
$N = W = m g = 7 \cdot 9.8 = 68.6 N$
From the first equation (alomg $x$) we get:
$F - {\mu}_{k} N = m a$
$F = \left(8 \cdot 68.6\right) + \left(7 \cdot 31\right) = 765.8 N$