Friction Quiz

1. A 20 kg box is on rough horizontal ground with $\mu=0.5$. What is the limiting friction?

• A. $196$ N
• B. $49$ N
• C. $98$ N
• D. $9.8$ N

2. A 10 kg box on a rough floor, $\mu=0.4$, is pushed horizontally with 30 N and does not move. What is the friction force?

• A. $39.2$ N
• B. $9.2$ N
• C. $0$ N
• D. $30$ N

3. A particle is on the point of slipping down a rough plane inclined at $35^\circ$. Find $\mu$.

• A. $0.574$
• B. $0.819$
• C. $0.700$
• D. $1.43$

4. A 2 kg particle on rough horizontal ground ($\mu=0.2$) is pushed by a 10 N horizontal force. Find its acceleration.

• A. $3.04\ \text{m s}^{-2}$
• B. $5.00\ \text{m s}^{-2}$
• C. $6.96\ \text{m s}^{-2}$
• D. $1.96\ \text{m s}^{-2}$

5. A block at rest on a rough surface is pushed by a horizontal force less than the maximum friction. Which statement is correct?

• A. $F=\mu R$ always
• B. $F$ equals the push, and $F<\mu R$
• C. $F=0$ until the block moves
• D. $F>\mu R$