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