Question

Please help.: Sliding from left to right in a straight line on a horizontal steel surface, an aluminum block weighing 20 newtons is acted on by a 2.4 newton friction force. The block will be brought to rest by the friction force in a distance of 10 meters. Determine the magnitude of the acceleration of the block as it is brought to rest by the friction force. (Show all work)

Answer 1

This can probably be done with kinematics or conservation of energy or a combination of both. Which do you prefer?

Answer 2

Kinematics would be the best I think

Answer 3

Ok, there is net force opposite the direction of motion, so acceleration is negative.
F=ma, so a=F/m. The net force is the friction, and the mass you can get from the weight (assuming we are near Earth's surface for W=mg).

Answer 4

Oh ok, I didn't know about the weight thing. So that would be 20N=m(-9.81) right?

Answer 5

Hmm, somehow, that seems too easy. I might be missing something..
but yes. mass = weight ÷ 9.81

Answer 6

Yeah, I'm trying to find the acceleration so maybe that is it. So the mass will be 2.039 approximately and then Fnet ( 0N I think) divided by 2.039..?

Answer 7

Can the acceleration be 0?

Answer 8

No, The net force is the 2.4N friction force and F=ma, so that should be all that's necessary.

Answer 9

Ok, thanks :D

Answer 10

The 10m travel distance isn't needed, but just in case I used it in the conservation of energy equation and it checks out.