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Friction, Q1. Fill in the blanks:, , 1. Friction always opposes _____ between the surfaces in contact with each other., (motion), , 2. Sliding friction is than static friction. (less), , , , 3. Friction produces ___. ( motion), 4. Friction prevent our foot from _____ over the ground. ( Slipping), 5. Sprinkling of powder on the carrom board friction. ( reduces), , 6. The friction when something moves through a liquid or gas is called____. ( Fluid, friction), , 7. Shapes that that are designed to reduce air resistance are called____ shapes., ( Streamline), , 8. The shape of an aeroplane is similar to that of a______in flight. ( bird), Q2. Answer in one sentence:, , 1, What type of surfaces produce least friction?, , Ans: The object that have smooth surfaces produce least friction., , 2. Why do Kabaddi Players from their hands with dry soil?, , Ans. Kabaddi Players rub their hands with dry soil to increase friction and get a better grip on, the opponent players, , 3. Name two common lubricants?, , Ans. The two common lubricants are oil and grease., , 4, What is done to increase friction between the tyres and Road?, , Ans: Treads are made in the tyres of vehicles to increase friction., , 5. Why are grooves provided in the soles of shoes?, , Ans: Grooves are made on the soles of shoes to to increase friction and prevent slipping., Q3. Answer the following questions:, , 1. Suppose your writing table is tilted a littlelittle. A book kept on it starts sliding down. Shov

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the direction of frictional force acting on it., , Ans: Friction acts opposite to the motion of the book., , b, Toy,, forge So, , , , 2. You spill a bucket of Soapy water on a marble floor accidentally. Would it make it easier or, more difficult for you to walk on the Floor? Why?, , Ans: a. It would be difficult to walk on the floor., , b. Soapy water fill the irregularities, thus reduces the friction., , c. Feet do not make necessary grip with the floor surface, thus increasing the chances of falling., 3. Explain why sportsmen use shoes with spikes?, , Ans: Spikes are the pointed nails which get into the ground and increase friction between shoe, and the ground. This prevents the slipping of player or athletes on running. Thus, sportsmen use, shoes with spikes., , 4. Iqbal has to push a lighter box and Seema has to push a similar heavier box on the same, floor. Who will have to apply a larger force and why?, , Ans: a. Seema will have to apply a larger force., b. This is because friction increases with the mass of object., , c. Heavier the box, more is the interlocking of irregularities between the two surfaces in, contact and hence more friction., , d. Thus, more force is required to push a heavier box than a lighter one., 5. Explain why the sliding friction is less than the static friction?, , Ans: a. When the object is at rest, the interlocking of irregularities in the two surfaces of the

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objects is higher than when the object are moving., , b. When objects are moving, there is less interaction between their surfaces. Thus, sliding, friction is less than static friction, , 6. Give examples to show that friction is both a friend and a foe?, Ans: The advantages of friction are as follows:, , a. Friction enables us to walk without slipping., , b. Friction enables a car to move on road without skidding., , c. Friction enables us to write and draw on paper., , d. Friction helps us to pick up and hold things in our hands., , The disadvantages of friction are as follows:, , a. Friction wears away the soles of shoes, the tyres of vehicles and the brake pads of vehicle., b. Friction produces heat which may damage machines., , c. Friction slows down motion., , 7. Explain why objects moving in Fluids have special shapes?, , Ans: a. The fluid friction can be reduced or minimised by giving special shape called streamlined, shape to the objects which move through fluids., , b. When an object having a streamlined body shape moves very fast, then the fluid can flow past, the moving object smoothly reducing the fluid friction., , This, the objects moving in Fluids have streamlined shape., Q8. What is drag? Give two examples of drag force? ., Ans: a The frictional force exerted by fluid is called drag., , b. The two examples of drag forces are the resistance force experienced by a car or an, aeroplane when they move at high speeds.