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प्रश्न
Sometimes, a crackling sound is heard while taking off a sweater during winters. Explain.
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उत्तर
When we take off our sweaters in winter, we hear a crackling sound. This is because removing our sweater acquires charge due to friction between the sweater and our body. As a result, we hear a crackling sound from the sweater.
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संबंधित प्रश्न
Friction depends on the ______ of surfaces.
Name the two kinds of forces in nature.
What is the cause of friction?
State two factors which directly affect the force of friction.
A body needs a force F1 just to start moving on a surface, a force F2 to continue its motion and a force F3 to roll on the surface. What is
- the static friction
- sliding friction and
- rolling friction? State whether F2 is equal, less than or greater than (1) F1 and (2) F3.
Answer the following.
What do you understand by a force?
Fill in the blank.
.................... is the SI unit of force.
Answer the following in detail.
What are the various effects of force? State one example of each.
Fill in the blank.
More the roughness of a surface, greater is the ........................
Fill in the blank.
The force of friction acting between two bodies in contact while at rest is known as ................ friction.
Tick the most appropriate answer.
Friction for an object can be reduced by
Fill in the blank.
Smoother the surface, ................. is the frictional force offered by it.
Answer the following in a word or two or in a sentence.
Why is difficult for a pen to leave a mark on a highly smooth plastic sheet?
Answer the following in detail.
Write the characteristics of the force of friction?
Answer the following in detail.
Describe three different ways by which friction can be increased to help us in various situations?
Match the following.
| Column I | Column II | |
| a) | Static friction | Viscosity |
| b) | Kinetic friction | Least friction |
| c) | Rolling friction | Objects are in motion |
| d) | Friction between the liquid layers | Objects are sliding |
| e) | Sliding friction | Objects are at rest |
Why is a ball bearing used in a cycle hub?
We have two identical metal sheets. One of them is rubbed with sand paper and the other with ordinary paper. The one rubbed with sand paper shines more than the other. Give reason.
Assertion: Friction always opposes the motion.
Reason: Whenever one surface moves or tries to move over another surface, the force of friction starts acting on the surfaces.
