Need physics help please?

Question

A block of mass M = 3 kg is released from rest and slides down an incline that makes an angle 32° with the horizontal. The coefficient of kinetic friction between the block and the incline is µk = 0.15.

a) What is the acceleration of the block down the inclined plane?

Answer 1

We'll need F=ma to find the acceleration. We have two forces acting though - one of gravity pulling the mass down the ramp, and one of friction resisting that pull.

The force of gravity runs parallel to the ramp, so we'll need to use some trig to find the force. Normally the force acting on the mass is

F = ma
F = (3 kg)(9.81 m/s^2)
F = 29.43 N

But since we're on an incline, we need to find the force along the ramp:

Fg = F * sin 32
Fg = 29.43 N * sin 32
Fg = 15.6 N

The force resulting from friction requires us to use the force of the mass acting perpendicular to the ramp. So,

Fn = F * cos 32
Fn = 29.43 N * cos 32
Fn = 24.96 N

Ff = µ * Fn
Ff = 0.15 * 24.96 N
Ff = 3.73 N

So the resulting force of the block is

Fr = Fg - Ff
Fr = 15.6 N - 3.73 N
Fr = 11.87 N

Finally, we can find the acceleration:

F = ma
11.87 N = 3 kg * a
a = 3.96 m/s^2

Answer 2

is this HS or college coursework?