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