# static friction

This is a problem which I am confused and able to solve So please tell me how to solve

A block of mass market is kept on an incline plane of a lift moving down with acceleration of 2m/s^-2 . What should be the coefficient of friction for the block to move down with constant velocity relative to lift

3 years, 6 months ago

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We have to use concept of pseudo force here.

First we shall consider a reference frame which is moving along with lift. As it is non-inertial frame of reference so we have to include a pseudo force here.

fig

Resolve the vectors in direction parallel to the plane and perpendicular to the plane. Then use newtons's second law to find equations.

If the block has to move with constant velocity then $$F_{net}=0$$.

Can you solve it from here?

- 3 years, 6 months ago

I solve as you told and I got the answer as 0.4 static friction can you tell this ans is right or wrong

- 3 years, 6 months ago

Could you please show your steps. I am getting its value slightly differently.

- 3 years, 6 months ago

Incline is at 30 ° so a= g sin 30°=5 So normal force = mg = 5m So the pseudo is acting as friction force here Then friction force (f)=static friction × normal force F=sf×5m 2m=sf×5m 2m/5m=sf 0.4= sf

- 3 years, 6 months ago

fig

From the diagram

$$N+2mcos\theta=mgcos\theta$$............(1)

and $$mgsin\theta=\mu N+2msin\theta$$ ...................(2)

Find N from eq(1) and put its value in eq(2). Then find $$\mu$$

- 3 years, 6 months ago

thank you for clearing the doubt

- 3 years, 6 months ago

You are welcome. :D

- 3 years, 6 months ago

Thanks you r the best

- 3 years, 6 months ago

Thanks!

- 3 years, 6 months ago