Question

An object with a mass of `12` `kg` is on a surface with a kinetic friction coefficient of `1`. How much force is necessary to accelerate the object horizontally at `7` `ms^-2`?

Answer 1

The total force is composed of two pieces: the force required to accelerate the mass and the force required to overcome friction. `F=ma+mumg=12*7+1*12*9.8=201.6` `N`.

Explanation:

The total force is made up of two different forces.

If there were no friction, the force required to accelerate a mass of `12` `kg` at an acceleration of `7` `ms^-2` is given by Newton's Second Law :

`F=ma=12*7=84` `N`

The second part is the frictional force:

`F_f=muF_N` where `mu` is the frictional coefficient and `F_N` is the normal force, which in turn is `mg`, the mass times the acceleration due to gravity.

`F_f=mumg=1*12*9.8=117.6` `N`

To find the total force, just add these two forces:

`F=ma+mumg=12*7+1*12*9.8=201.6` `N`.