Ncert – class 8- science – Chapter 9: Friction2 Welcome to your Ncert - class 8- science - Chapter 9: Friction2 1. A car will skid more on a wet road than on a dry road and the car tyres there is more: heat lubricant gravity friction None 2. 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 3. 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: d > b > a > c a > b > c > d b > c > d > a c > b > d > a None 4. 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 5. Why are efforts made to reduce friction Energy is lost in overcoming friction. Both A and B None of the above Overcoming friction is a time consuming process. None 6. 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 7. What measures are taken to reduce fluid friction in aeroplanes? Metals are choosen in a way to make the aeroplane lighter with smoother surface Streamlined body inspired by birds All of the above Optimum speed is maintained with respect to the air None 8. 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 suffers zero air friction the muzzle suffers less air friction none of these the muzzle tears apart the air layers and suffers more air friction None 9. When two surfaces are coated with lubricant, then they will: roll upon each other stick to each other slide upon each other jump on each other None 10. Boats and aeroplanes are ................. so as to reduce fluid friction.fill in the blank. bigger broader large streamlined None 11. Friction can be increased by increasing: Grease on the surface Lubricating the surface Roughness of the surface Smoothness of the surface None 12. 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 rolling friction sliding friction static friction None 13. When a body is moving on a surface, the force of friction is called Kinetic friction Rolling friction Static friction Limiting friction None 14. When two surfaces are coated with lubricant, then they will: stick to each other jump on each other roll upon each other slide upon each other None 15. Unevenness in the surfaces of the moving body and the surface on which it moves causes: centripetal force gravitational force centrifugal force frictional force 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.
