Friction doubt!

A small block of mass mm is kept at the left end of a larger block of mass MM and length ll . The system is started towards right with an initial velocity vv . The friction coefficient between the road and the bigger block is kk and that between the blocks is k/2k/2 . Find the time elapsed before the smaller block separates from the bigger block?

I am having hard time solving this , can somebody please help ,if possible with an FBD.

Thanks!

Note by Shivam Mishra
3 years, 4 months ago

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@Deeparaj Bhat Please help!!!!

shivam mishra - 3 years, 4 months ago

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On the smaller block, the friction is towards the left (assuming the velpcity is towards the right).

On the bigger block, the friction at the contact surface of the smaller block is towards right (Newton's third law) and the friction at the ground surface is towards left.

Hope this helps!

Deeparaj Bhat - 3 years, 4 months ago

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So, will the smaller block move the total length of bigger block and then fall or it will just slip towards the left after some time interval?

shivam mishra - 3 years, 4 months ago

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@Shivam Mishra It'll move the total length if M>mM>m.

Deeparaj Bhat - 3 years, 4 months ago

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@Deeparaj Bhat So,for the block with mass MM what would be the for net force of friction acting?

shivam mishra - 3 years, 4 months ago

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@Shivam Mishra For the block with mass MM, Net force in horizontal direction is given by Mgkmgk2Mgk-mg\dfrac{k}{2} towards the left (opposite to direction of vv ).

For the block with mass mm, net horizontal force (opposite to direction of vv) is mgk2mg\dfrac{k}{2}.

Deeparaj Bhat - 3 years, 4 months ago

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@Deeparaj Bhat But how can the force on MM be towards left when the system in supposed to move towards right?

shivam mishra - 3 years, 4 months ago

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@Shivam Mishra Friction is always against relative motion. So, as the system goes towards right and the ground is stationary, friction acts towards left.

Deeparaj Bhat - 3 years, 4 months ago

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@Deeparaj Bhat OK thanks for help!!!! I am horrible at physics

shivam mishra - 3 years, 4 months ago

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@Shivam Mishra You're welcome. :)

Deeparaj Bhat - 3 years, 4 months ago

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@Deeparaj Bhat can you please tell how did you come to know that the smaller block would move on the bigger block just by considering M>m ?

A Former Brilliant Member - 3 years, 3 months ago

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