Ncert – class 8- science – Chapter 9: Friction2 Welcome to your Ncert - class 8- science - Chapter 9: Friction2 1. Match the followingList IList II1. Streamlined body structurea. Less no. of irregularities2. Pressing two objects harder against each otherb. Lubricant3. Greasec.Increase friction 4. Smooth surfaced. Decrease friction 1-a, 2-d, 3-b, 4-c 1-d, 2-c, 3-b, 4-a 1-d, 2-c, 3-a, 4-b 1-a, 2-b, 3-c, 4-d None 2. Unevenness in the surfaces of the moving body and the surface on which it moves causes: gravitational force centripetal force frictional force centrifugal force None 3. Frictional force increases when surfaces in contact are made very smooth, because of Decrease in irregularities Decrease in surface area Increase in area Molecular force None 4. If we drop a cup of water on a plate and a cup of oil on another plate, water is seen to spread faster along diameter. This is an example related to: fluid friction sliding friction rolling friction static friction None 5. Friction can be increased by increasing: Lubricating the surface Smoothness of the surface Grease on the surface Roughness of the surface None 6. A ball is rolled on four surfaces:a) marble floor, b) on sand, c) on cloth, d) on wood.The force of friction acting on the ball on these different surfaces in descending order will be: a > b > c > d d > b > a > c c > b > d > a b > c > d > a None 7. Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be Newspaper, towel, dry marble floor, wet marble floor Wet marble floor, dry marble floor, newspaper and towel. Wet marble floor, dry marble floor, towel, newspaper Towel, newspaper, dry marble floor, wet marble floor None 8. A car will skid more on a wet road than on a dry road and the car tyres there is more: heat gravity friction lubricant None 9. Why are efforts made to reduce friction Overcoming friction is a time consuming process. Energy is lost in overcoming friction. Both A and B None of the above None 10. What measures are taken to reduce fluid friction in aeroplanes? Streamlined body inspired by birds Metals are choosen in a way to make the aeroplane lighter with smoother surface Optimum speed is maintained with respect to the air All of the above None 11. When a body is moving on a surface, the force of friction is called Limiting friction Rolling friction Static friction Kinetic friction None 12. After an aeroplane completes a voyage, its muzzle feels warmer than the middle and back portion of the main body. This is because: the muzzle tears apart the air layers and suffers more air friction the muzzle suffers less air friction the muzzle suffers zero air friction none of these None 13. When two surfaces are coated with lubricant, then they will: slide upon each other jump on each other roll upon each other stick to each other None 14. Boats and aeroplanes are ................. so as to reduce fluid friction.fill in the blank. large streamlined bigger broader None 15. When two surfaces are coated with lubricant, then they will: stick to each other slide upon each other jump on each other roll upon each other None Time's up Please Share This Share this content Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Leave a Reply Cancel replyCommentEnter your name or username to commentEnter your email address to commentEnter your website URL (optional) Save my name, email, and website in this browser for the next time I comment.
