Q

# Solve it, Given in the figure are two blocks A and B of weight 20 N and 100 N, respectively. These are being pressed against a wall by a force F as shown. If the coefficient of friction between the blocks is 0.1 and between block B and the wall is 0. Given in the figure are two blocks A and B of weight 20 N and 100 N, respectively. These are being pressed against a wall by a force F as shown.  If the coefficient of friction between the blocks is 0.1 and between block B and the wall is 0.15, the frictional force applied by the wall on block B is :

• Option 1)

100 N

• Option 2)

80 N

• Option 3)

120 N

• Option 4)

150 N

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As we learnt in

Motion of Block in Contact - - wherein

Static Friction -

Self adjusting force because it changes itself according with the applied force. - wherein

It always equal to net external force. Static friction (F = P) using diag. N = F

fr1 = 20 N

fr2 = 100 + 20 = 120 N Where assume two blocks as one system due to equilibrium.

fr =120 N

Correct option is 3.

Option 1)

100 N

This is an incorrect option.

Option 2)

80 N

This is an incorrect option.

Option 3)

120 N

This is the correct option.

Option 4)

150 N

This is an incorrect option.

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