Question

sd

Answer 1

Hello! First thing's first. Does the problem seem to give you anywhere to start?

Answer 2

Are you there?

Answer 3

Well, first, you need to understand friction. It is a force that opposes motion, and comes into play where surfaces are in contact.

The "uk," or \(\mu_k\), is the coefficient of \(k\)inetic friction. A coefficient is just something that multiplies something!

Here, the \(f\)riction force is a coefficient that multiplies the \(n\)ormal force, which is the force that the surface pushes up on your block.
\(F_f=\mu_kF_n\)

So, the block is probably experiencing that friction force.

What is \(F_n\), the normal force? Well, what force has to hold the block up? Think "equal and opposite," the Newton's third law.


Once you find the friction force, you will have the net force. Thus, you can find the acceleration with Newton's second law.

Then you can use a kinematic equation for part 2.

Good luck!

Answer 4

isn't acceleration 0? since velocity constant?

Answer 5

Velocity isn't constant. That was the initial velocity, I think. Then friction slows it down.

The question was to find acceleration and stopping distance if \(\mu_k=0.9\), right? That coefficient makes there be friction that is a force that causes the block's acceleration. Then
\(v_f^2=v_i^2+2ad\) would be appropriate.