Ncert – class 8- science – Chapter 9: Friction2 Welcome to your Ncert - class 8- science - Chapter 9: Friction2 1. Why are efforts made to reduce friction None of the above Energy is lost in overcoming friction. Both A and B Overcoming friction is a time consuming process. None 2. 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: b > c > d > a a > b > c > d d > b > a > c c > b > d > a None 3. 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 4. Friction can be increased by increasing: Roughness of the surface Grease on the surface Smoothness of the surface Lubricating the surface None 5. A car will skid more on a wet road than on a dry road and the car tyres there is more: heat lubricant friction gravity None 6. 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 zero air friction the muzzle suffers less air friction none of these None 7. Frictional force increases when surfaces in contact are made very smooth, because of Increase in area Molecular force Decrease in irregularities Decrease in surface area None 8. 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: static friction sliding friction fluid friction rolling friction None 9. Boats and aeroplanes are ................. so as to reduce fluid friction.fill in the blank. bigger broader large streamlined None 10. 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 11. 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-a, 4-b 1-a, 2-b, 3-c, 4-d 1-d, 2-c, 3-b, 4-a None 12. When two surfaces are coated with lubricant, then they will: slide upon each other stick to each other roll upon each other jump on each other None 13. 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 14. 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, newspaper and towel. Newspaper, towel, dry marble floor, wet marble floor Wet marble floor, dry marble floor, towel, newspaper None 15. When a body is moving on a surface, the force of friction is called Static friction Rolling friction Limiting friction Kinetic 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.
