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