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