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