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