Ncert – class 8- science – Chapter 9: Friction 1 Welcome to your Ncert - class 8- science - Chapter 9: Friction 1 1. Tick the most appropriate answer:Force of friction comes into play when a/an All of the these Moving object tries to stop Object is at rest Object attempts motion None 2. Brakes of a very small contact area are not used, although friction is independent of area. It is because friction: causes wear and tear operating in this case is sliding friction resists motion depends on the nature of the material None 3. Galileo did his experiments on inclined planes with smooth surfaces and observed that As smoother the surface, the farther the ball traveled As rough the surface, the farther the ball traveled As smoother the surface, the nearer the ball traveled None of these None 4. A ball moving on ground eventually stops. Mark the correct reason Because an object in motion should come to rest no matter what Because no external force is applied on the ball by the surface None of these Because of frictional force between ball and the ground None 5. Mark the correct statement: Frictional force also exist when there is no motion. Frictional force is nothing but the weight of the body None Frictional force only exist when there is motion between two objects. None 6. Tick the most appropriate answer:If you pour some oil onto a floor, the friction would Remain the same None of these Decrease Increase None 7. Frictional force between two surface in contact is due the Both 2 and 3 Cohesive force between the molecules Repulsive forces between the molecules Adhesive force between the molecules None 8. When two surfaces are coated with a lubricant, then they. Slide upon each other Roll upon each other None of these Stick to each other None 9. Read the given statements and select the correct option.Statement 1 : It takes a much longer time and covers more distance to stop a moving ship in water than a moving car with same speed on the road.Statement 2 : The friction on water surface is much less than the solid surface. Both statements 1 and 2 are true and statement 2 is not the correct explanation of statement 1. Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1. Statement 1 is false but statement 2 is true. Statement 1 is true but statement 2 is false. None 10. The interlocking of the depressions and elevations (irregularities) present on the surfaces of the bodies in contact cause friction. True Ambiguous False Data Insufficient None 11. Which one of the following can also act as a lubricant in machines? Flow of water through the machine Iron filling Flow of compressed and purified air. Polish on machines None 12. When walking on ice, one should take small steps to avoid slipping. Smaller steps help avoid slipping because they result in: A larger normal force. Larger friction with the ice. Smaller friction with the ice. A smaller normal force. None 13. In cold weather, we rub our hands to warm them. The force involved in this is: Static force. Gravitational force. Friction force. Electrostatic force. None 14. Friction for an object can be reduced by: Streamlining Lubricating All of the above Providing wheels None 15. Why are vehicle tires treaded? To decrease friction. To increase friction. To multiply friction. To decrease grip. None 16. When a ball is left rolling on ground it stops after some time.What bring the rolling ball to rest? Air drag Force of friction Gravitational force Buoyant force None 17. If the outer surface of a glass tumbler is greasy. it would become Easier to hold it because friction get increased Easier to hold it because friction get reduced Difficult to hold it, because friction get reduced Difficult to hold it, because friction get increased None 18. Select the correct alternative:Friction is increased if The surfaces are made dry The surface are made wet An oil is sprayed The surfaces are polished None 19. Tick the most appropriate answer:A car skids on a wet or muddy road due to Lubrication of brakes on a wet road Reduced friction between the road and the tyres Increased friction between the road and the tyres Streamlined shape of the car None 20. Which of the following is not an example of force acting at a distance ? Force of gravity Magnetic force Electric force Frictional force 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.
