Friction
Table of Contents
Whenever a body moves or tends to move over the surface of another body, a force comes into play which acts parallel to the surface of contact and opposes the relative motion. This opposing force is called friction.
Angle of friction
The angle of friction may be defined as the angle which the resultant of the limiting friction and the normal reaction makes with the normal reaction.
Angle of repose
It is the minimum angle that an inclined plane makes with the horizontal when a body placed on it just begins to slide down.
Numerical Problems Based on Class 11 Physics Friction
Q.1. A suitcase is gently dropped on a conveyor belt moving at 3 ms-1. If the coefficient of friction between the belt and the suitcase is 0.5, how far will the suitcase move on the belt before coming to rest?
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Answer: 0.92 mQ.2. A block of mass 1 kg lies on a horizontal surface in a truck. The coefficient of static friction between the block and the surface is 0.6. If the acceleration of the truck is 5 ms-2, calculate the frictional force acting on the block.
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Answer: 5 NQ.3. Find the distance travelled by a body before coming to rest, if it is moving with a speed of 10 ms-1 and the coefficient of friction between the ground the body is 0.4.
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Answer: 12.75 mQ.4. A bullet of mass 10 g is fired horizontally into a 5 kg wooden block, at rest on a horizontal surface. The coefficient of kinetic friction between the block and the surface is 0.1. Calculate speed of the bullet striking the block, if the combination moves 20 m before coming to rest.
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Answer: 3136.26 m/sQ.5. A scooter weighs 120 kg f. Brakes are applied so that wheels stop rolling and start skidding. Find the force of friction if the coefficient of friction is 0.4.
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Answer: 48 kg fQ.6. Find the force required to move a train of mass 105 kg up an incline 1 in 50 with an acceleration of 2 ms-2. Coefficient of friction between the train and the rails is 0.005. Take g = 10 ms-2.
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Answer: 2.25 x 105 NQ.7. A block of mass 2 kg rests on a plane inclined at an angle of 30° with the horizontal. The coefficient of friction between the block and the surface is 0.7. What will be the frictional force acting on the block?
The correct answer of question number 07 is 9.8 Newton.