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