# Newtons Third Law Problem

Figure shows a block of mass resting on a slope. The block has coefficients of friction and with the surface. It is connected via a massless string over a massless, frictionless pulley to a hanging block of mass 2.0 kg.
i got this first one: What is the minimum mass that will stick and not slip?

1.83 kg
Correct

But can't get the second part:
If this minimum mass is nudged ever so slightly, it will start being pulled up the incline. What acceleration will it have? Thank you! :)

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ehild
Homework Helper
Figure shows a block of mass resting on a slope. The block has coefficients of friction and with the surface.

Correct the sentence in red please. What are the coefficients of friction?

ehild

PeterO
Homework Helper
Figure shows a block of mass resting on a slope. The block has coefficients of friction and with the surface. It is connected via a massless string over a massless, frictionless pulley to a hanging block of mass 2.0 kg.
i got this first one: What is the minimum mass that will stick and not slip?

1.83 kg
Correct

But can't get the second part:
If this minimum mass is nudged ever so slightly, it will start being pulled up the incline. What acceleration will it have? Thank you! :)
Once the block starts moving, the coefficient of friction is then the kinetic coefficient, which will mean a smaller friction. Thus there is a net force up the slope [and down on the hanging mass] which causes the system to accelerate.

I'm really sorry about that ehild! The mu(s) is .8 but the mu(k) which I assume we use on this problem because it's moving therefore kinetic is .5 =-)

Once the block starts moving, the coefficient of friction is then the kinetic coefficient, which will mean a smaller friction. Thus there is a net force up the slope [and down on the hanging mass] which causes the system to accelerate.
Thank you Peter!

ehild
Homework Helper
I'm really sorry about that ehild! The mu(s) is .8 but the mu(k) which I assume we use on this problem because it's moving therefore kinetic is .5 =-)
Everything is clear then. Can you solve the second part or still need help?

ehild

Everything is clear then. Can you solve the second part or still need help?

ehild
Yes, it's clear. Thank you ehild! :)