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 is greater than sliding friction.
• B. Sliding friction is greater than static friction
• C. No frictional force acts after the cart comes in motion.
• D. Air friction is greater during first few steps of motion.

Answer 1

Answer: (A)

Static friction is greater than sliding friction.

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.