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## #1 2014-08-22 04:47:44

niharika_kumar
Member
From: Numeraland
Registered: 2013-02-12
Posts: 1,062

### find the force

In this figure, mass M is fixed on the wall.How much force on mass m=5 kg should be applied so that it won't slip.
(given: acceleration of van=5m/s^2 ;coefficient of friction between m and M=0.4)

Pls help.

Last edited by niharika_kumar (2014-08-22 04:48:09)

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## #2 2014-08-22 13:45:39

Agnishom
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From: Riemann Sphere
Registered: 2011-01-29
Posts: 24,838
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### Re: find the force

The reaction force between m and M is 5kg*5m/s^2

To balance the friction, you must give a force of 5kg*5m/s^2*0.4

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## #3 2014-08-22 19:15:19

niharika_kumar
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From: Numeraland
Registered: 2013-02-12
Posts: 1,062

### Re: find the force

I thought the the same but it is an MCQ question with options as follows:-

a)170 N
b)180 N
c)150 N
d)250 N

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## #4 2014-08-22 23:24:25

Olinguito
Member
Registered: 2014-08-12
Posts: 649

### Re: find the force

Weight of m (taking
) is
.

So the frictional force required to keep m from slipping is
.

This can be supplied by a horizontal force of
.

Now the van is accelerating to the right, meaning m would be accelerating to the left relative to the van with a force of
.

Therefore the horizontal force required to pin m to M is
.

NB: The 150 N horizontal force consists of 25 N required to keep m stationary relative to the van and 125 N needed to generate the frictional force to balance its weight.

Last edited by Olinguito (2014-08-22 23:39:15)

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## #5 2014-08-23 03:22:34

niharika_kumar
Member
From: Numeraland
Registered: 2013-02-12
Posts: 1,062

### Re: find the force

wow, you explained it so easily and well.(It reminded me of bob.)

thank you

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