Week end assignment
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Class:8
Sub. : Science
Answer the following questions briefly.
1) What is friction?
2) What is the shape of the body of the fish in water?
3) What are static and sliding friction?
4)Explain why sportsmen use shoes with spikes?
5) Give examples to show that friction is both a friend and a foe.
6) Explain why sliding friction is less than static friction?
7) Explain why objects moving in fluids must have special shape?
8) If you try to hold a glass with soapy hands,it can easily slip from your hand.Why?
9) When you play a game of carrom what do you do to make the coins move smoothly on the board?
10) What are Lubricants? How are they useful?
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Answers
Answer:
1) friction is the resistance to the motion of an object
2) streamlined
3) static friction is the friction which don't let a body move
sliding friction is enacted when a body rolls over the another
4) to have a better grip on the ground
5) friction causes wear and tear which damages the machine
friction helps us to walk or hold objects
6) because of the amount of relative motion between two surfaces
7) to reduce the effect of fluid friction in them
8) because friction is decreased as the soap particles act as a lubricant
9) sprinkle powder on the board
10) lubricants are the substances used to reduce friction
they are useful to reduce friction
Explanation:
Answer:
Explanation:
1 Friction is a force between two surfaces that are sliding, or trying to slide, across each other. ... Friction always slows a moving object down.
2 The shape of a fish helps it hunt for prey and avoid predators. A torpedo-shaped body increases a fish's swimming speed. Most fish with this shape live in open water and are excellent swimmers.
3 Static, sliding, and rolling friction occur between solid surfaces. Static friction is strongest, followed by sliding friction, and then rolling friction, which is weakest. Fluid friction occurs in fluids, which are liquids or gases.
4 Sportsmen use shoes with spikes so as to have a better grip while running. This is because the force of friction between the shoes and the ground increases with the help of spikes.
5 friction causes wear and tear in objects.
6 sliding friction is slightly lesser than that of the static friction because it is easy to move the object which already in motion than the object which is at rest.
7 Objects moving in fluids face the friction of the fluid that opposes their motion. So Objects moving in fluids must have unique shapes called streamlined shapes to reduce the fluid friction.
9 We sprinkle powder on carrom board to make the surface of the board smooth. This reduces the friction between the surface of the carrom board, the striker and the coins. As a result, the coins and the striker can move easily on the carrom board.
10 A lubricant is a substance, usually organic, introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces.
8it is because glass has a smooth surface.so there will be less friction and soapy hands also have less friction.so while holding friction is less so it tends to slip!