Question

Case I: A block of mass 1 kg is placed on a rough horizontal surface.
Case II: A block of mass 1 kg is placed on a rough horizontal surface and another identical block is kept over it.
Choose the correct statement.

• A. Static friction acting in case I is greater than that in case II.
• B. Static friction acting in case I is less than that in case II.
• C. Static friction acting in case I is equal to that in case II and is non-zero.
• D. No friction is acting in both cases.

Answer 1

The correct option is D No friction is acting in both cases.

Static friction comes into picture only when there is a tendency of relative motion between surfaces in contact. Here, in both the cases, no external force is acting in horizontal direction. Hence, no friction will act on the blocks.