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