Guest

a block of mass 2 kg is pushed against a rough vertical wall with a force of 40N,coeff of static friction=0.5..another horizontal force of 15N,is applied on block in a direction parellel to wall.will the block move?if yes, in which direction?if no,find frictional force exerted by wall on block.

a block of mass 2 kg is pushed against a rough vertical wall with a force of 40N,coeff of static friction=0.5..another horizontal force of 15N,is applied on block in a direction parellel to wall.will the block move?if yes, in which direction?if no,find frictional force exerted by wall on block.

Grade:11

4 Answers

Badiuddin askIITians.ismu Expert
148 Points
14 years ago

Dear Tushar

max static friction force that can be exerted by wall on block is =0.5*40 =20 N


since applied horizontal force 15 N is less than max static force so block will not move


so friction force exerted by wall on block is =15 N


Please feel free to post as many doubts on our discussion forum as you can.
 If you find any question Difficult to understand - post it here and we will get you the answer and detailed solution very quickly.
 We are all IITians and here to help you in your IIT JEE  & AIEEE preparation.

 All the best.
 
Regards,
Askiitians Experts
Badiuddin

RAJEEV CHOUDHARY
9 Points
14 years ago

Sir,

     There are 2 forces parallel to wall,one vertical due to gravitation(20 N) and another horizontal force of 15 N.Now friction will oppose both of them so we shoudnt ignore gravitation force in calculation of friction.Force due to gravitation was there before exerting horizontal force of 15 N so friction in vertical direction is 20 N.Now as we apply horizontal force of 15 N there will be no friction opposing it so block will move in that direction.This is one fo my approach.

Another one(it may be vague) is that we can distribute max. friction in both directions proportion to the forces exerted in those directions.But i am nt sure abt this method.

plz clarify my doubts. 

RAJEEV CHOUDHARY
9 Points
14 years ago

Sir,

If we assume that block is at a height from the ground then we should include gravitation force also  in calculation of friction.There are 2 forces in perpendicular direction.One weight of 20 N and another horizontal force of 15 N.Before exertion of 15 N force weight waas there so friction of 20 N will be there to balance the weight.Now as we apply horizontal force of 15 N there will be no friction to balance as it max friction itself is 20 N which is balancing the weight.So block will move in the direction of horizontal  force with acceleration of 7.5 m/sec2.

plz clear my doubts.

Aman Raj
15 Points
5 years ago
Total external force is 25N, and max limiting friction is 20N. So block will move making an angle of 53 degree with  15N (force parallel to wall) 

Think You Can Provide A Better Answer ?

ASK QUESTION

Get your questions answered by the expert for free