Friction Questions and Answers Part-3

1. If a ladder weighing 250 N is placed against a smooth vertical wall having coefficient of friction between it and floor is 0.3, then what is the maximum force of friction available at the point of contact between the ladder and the floor
a) 75 N
b) 50 N
c) 35 N
d) 25 N

Answer: a
Explanation: 75 N

2. Which one of the following statements is correct
a) Rolling friction is greater than sliding friction
b) Rolling friction is less than sliding friction
c) Rolling friction is equal to sliding friction
d) Rolling friction and sliding friction are same

Answer: b
Explanation: Rolling friction is less than sliding friction

3. The maximum speed that can be achieved without skidding by a car on a circular unbanked road of radius R and coefficient of static friction \[\mu \], is
a) \[\mu Rg \]
b) \[ Rg\sqrt{\mu} \]
c) \[ \mu\sqrt{ Rg} \]
d) \[ \sqrt{\mu Rg} \]

Answer: d

4. A car is moving along a straight horizontal road with a speed \[v_{0}\] . If the coefficient of friction between the tyres and the road is \[\mu \], the shortest distance in which the car can be stopped is
a) \[\frac{v_0^2}{2\mu g}\]
b) \[\frac{v_{0}}{\mu g}\]
c) \[\left(\frac{v_{0}}{\mu g}\right)^{2}\]
d) \[\frac{v_{0}}{\mu }\]

Answer: a

5. A block of mass 5 kg is on a rough horizontal surface and is at rest. Now a force of 24 N is imparted to it with negligible impulse. If the coefficient of kinetic friction is 0.4 and \[g=9.8 m\diagup s^{2}\]  , then the acceleration of the block is
a) \[0.26 m\diagup s^{2}\]
b) \[0.39 m\diagup s^{2}\]
c) \[0.69 m\diagup s^{2}\]
d) \[0.88 m\diagup s^{2}\]

Answer: d

6. A body of mass 2 kg is being dragged with uniform velocity of 2 m/s on a rough horizontal plane. The coefficient of friction between the body and the surface is 0.20. The amount of heat generated in 5 sec is ( J = 4.2 joule / cal and g = 9.8 m/s2)
a) 9.33 cal
b) 10.21 cal
c) 12.67 cal
d) 13.34 cal

Answer: a

7. Two carts of masses 200 kg and 300 kg on horizontal rails are pushed apart. Suppose the coefficient of friction between the carts and the rails are same. If the 200 kg cart travels a distance of 36 m and stops, then the distance travelled by the cart weighing 300 kg is
a) 32 m
b) 24 m
c) 16 m
d) 12 m

Answer: c

8. A body B lies on a smooth horizontal table and another body A is placed on B. The coefficient of friction between A and B is \[\mu\]. What acceleration given to B will cause slipping to occur between A and B
a) \[\mu g\]
b) \[g\diagup\mu\]
c) \[\mu\diagup g\]
d) \[\sqrt{\mu g}\]

Answer: a

9. A 60 kg body is pushed with just enough force to start it moving across a floor and the same force continues to act afterwards. The coefficient of static friction and sliding friction are 0.5 and 0.4 respectively. The acceleration of the body is
a) 6 \[m\diagup s^{2}\]
b) 4.9 \[m\diagup s^{2}\]
c) 3.92 \[m\diagup s^{2}\]
d) 1 \[m\diagup s^{2}\]

Answer: d

10. A car turns a corner on a slippery road at a constant speed of 10 m/s . If the coefficient of friction is 0.5, the minimum radius of the arc in meter in which the car turns is
a) 20
b) 10
c) 5
d) 4

Answer: a