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प्रश्न
Answer in short.
State the laws of kinetic friction.
उत्तर
- First law: The force of kinetic friction (Fk) is directly proportional to the normal reaction (N) between two surfaces in contact.
Fk ∝ N
∴ Fk = μk N
where, μk = constant called the coefficient of kinetic friction. - Second law: Force of kinetic friction is independent of shape and apparent area of the surfaces in contact.
- Third law: Force of kinetic friction depends upon the nature and material of the surfaces in contact.
- Fourth law: The magnitude of the force of kinetic friction is independent of the relative velocity between the object and the surface provided that the relative velocity is neither too large nor too small.
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संबंधित प्रश्न
Answer in one sentence.
Define friction.
Answer in one sentence.
Why force of static friction is known as ‘self-adjusting force’?
Answer in one sentence.
Name two factors on which the coefficient of friction depends.
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Answer in short.
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Explain how lubricants help in reducing friction.
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State the laws of static friction.
Answer in short.
State advantages of friction.
State disadvantages of friction.
Long answer type question.
Define coefficient of static friction and coefficient of kinetic friction. Give the necessary formula for each.
Calculate the coefficient of static friction for an object of mass 50 kg placed on horizontal table pulled by attaching a spring balance. The force is increased gradually it is observed that the object just moves when spring balance shows 50 N.
Answer the following.
A block of mass 37 kg rests on a rough horizontal plane having coefficient of static friction 0.3. Find out the least force required to just move the block horizontally.
A body of mass 37 kg rests on a rough horizontal surface. The minimum horizontal force required to just start the motion is 68.5 N. In order to keep the body moving with constant velocity, a force of 43 N is needed. What is the value of coefficient of static friction?
