C. Short answer questions. 1. What is a friction force? Why does it oppose a motion? 2. Why do we fall down when we step on a banana peel? 3. Distinguish between static and sliding friction. 4. Which factors affect the friction between two surfaces? 5. What do you mean by interlocking of irregularities? 6. What are the disadvantages of heat produced by friction in machines? 7. What are lubricants? List some of their uses. 8. What is rolling friction? Why is wheel considered a great invention?
Answers
Answer:
1.You must apply a certain amount of force to the box to keep it moving. The force that acts against your pushing force is called friction. is a force that resists the motion between two surfaces in contact. When you try to slide two surfaces across each other, the force of friction resists the sliding motion.
2.To have a solid grip, we want a good amount of frictional force between our feet and the surface. But if somehow, if we step on a banana peel, the frictional force between the surface and the feet suddenly decreases and we slip and tend to fall.
3.Static friction takes place whenever two bodies don't have a rotational speed, whilst also sliding friction occurs whenever the two different substances have a rotational speed.
5.Friction is a result of interlocking. Every object has some irregularities or roughness on its surface. The irregularities on surfaces result in interlocking of two surfaces. Friction depends on the irregularities of surfaces.
4.The factors that affect the friction between two surfaces are the weight of the object and the coefficient of friction of the surface.
6.Disadvantages of friction: Friction produces a lot of heat in various parts of the machinery and this leads to wastage of energy as heat. Opposes motion, hence more energy is needed to overcome friction. Noise production in machines is irritating as well as leads to energy loss.
7.Lubricant is a substance which is used to control (more often to reduce) friction and wear of the surfaces in a contact of the bodies in relative motion [1]. Depending on its nature, lubricants are also used to eliminate heat and wear debris, supply additives into the contact, transmit power, protect, seal.
8.The invention of wheel is considered as an important step of development in the history of science because wheel forms rotational motion which is less than sliding friction. Thats why it's easy step for transportation. E.g :- whole car rotates it's stearing to turn it's direction .