Question

A man tries to remain in a steady state by pushing his feet and hands against two parallel walls. Then for equilibrium:

• A. force of friction should be equal on the two walls
• B. Friction must be present on both walls
• C. coefficient of friction should be equal for both walls and the man
• D. none of the above

Answer 1

The correct option is B Friction must be present on both walls

According to Newton's third law when he applies a force on one wall, he should apply same force to the other wall for equilibrium. but the wall should not be frictionless otherwise he will fall down.
For equilibrium the forces exerted by both walls on the man should be equal so as the horizontal forces may balance but the vertical forces can be balanced even if the forces of friction on the two walls are unequal.
Ans:(B)