Ncert – class 8- science – Chapter 9: Friction 1 Welcome to your Ncert - class 8- science - Chapter 9: Friction 1 1. 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 2. Tick the most appropriate answer:Force of friction comes into play when a/an Moving object tries to stop Object is at rest All of the these Object attempts motion None 3. In cold weather, we rub our hands to warm them. The force involved in this is: Gravitational force. Static force. Friction force. Electrostatic force. None 4. 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 increased Difficult to hold it, because friction get reduced None 5. 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 6. When a ball is left rolling on ground it stops after some time.What bring the rolling ball to rest? Force of friction Gravitational force Buoyant force Air drag None 7. Tick the most appropriate answer:If you pour some oil onto a floor, the friction would Increase Decrease None of these Remain the same None 8. Why are vehicle tires treaded? To decrease grip. To decrease friction. To multiply friction. To increase friction. None 9. 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 10. Select the correct alternative:Friction is increased if The surface are made wet The surfaces are made dry The surfaces are polished An oil is sprayed None 11. When two surfaces are coated with a lubricant, then they. None of these Slide upon each other Roll upon each other Stick to each other None 12. Tick the most appropriate answer:A car skids on a wet or muddy road due to Reduced friction between the road and the tyres Streamlined shape of the car Lubrication of brakes on a wet road Increased friction between the road and the tyres None 13. Friction for an object can be reduced by: All of the above Lubricating Providing wheels Streamlining None 14. The interlocking of the depressions and elevations (irregularities) present on the surfaces of the bodies in contact cause friction. Ambiguous False Data Insufficient True None 15. Which of the following is not an example of force acting at a distance ? Frictional force Electric force Force of gravity Magnetic force 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. 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. Both statements 1 and 2 are true and statement 2 is the correct explanation of statement 1. None 17. 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 operating in this case is sliding friction causes wear and tear resists motion None 18. A ball moving on ground eventually stops. Mark the correct reason None of these Because an object in motion should come to rest no matter what Because of frictional force between ball and the ground Because no external force is applied on the ball by the surface None 19. Galileo did his experiments on inclined planes with smooth surfaces and observed that None of these As smoother the surface, the nearer the ball traveled As smoother the surface, the farther the ball traveled As rough the surface, the farther the ball traveled None 20. Which one of the following can also act as a lubricant in machines? Polish on machines Flow of water through the machine Flow of compressed and purified air. Iron filling 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.
