Question

& IB
FRICTION
14. Every surface is rough and system is at rest choose correct options
2m
a) Friction on m is mg upwards
c) Friction on 2m is 2mg upwards
b) Friction on 2m by wall is 3mg upwards
d) Friction on 2m by m is mg downwards
15. Two blocks​

Answer 1

Answer:

option b is correct as the block has tendency to slip downwards and both the blocks can be considered as system so normal is 3mg and friction is upwards

Answer 2

The options a,b,d is correct.

a) Friction on m is mg upwards

   On mass m, the gravitational force acts downward and due to that friction force acts upwards which is

     f1 = mg and the direction is upward.

Hence, option a is correct.

b) Friction on 2m by wall is 3mg upwards

The friction on 2m by the wall will be equal to the sum of both mg and 2mg gravitational forces acting downwards.

     f2 = mg + 2mg

          = 3mg

Hence, option b is correct.

c) Friction on 2m is 2mg upwards

it is the same as option 2, so it should be 3mg upward

     f = 3mg and the direction is upward.  

Hence, option c is incorrect.

d) Friction on 2m by m is mg downwards

this is similar to 1, The friction on mass 2m by m is the gravitational force acts downward and due to that friction force acts upwards which acts downward on mass 2m.

         f4 = mg and acting downward.

Hence, option d is correct

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