Ncert – class 8- science – Chapter 9: Friction 1 Welcome to your Ncert - class 8- science - Chapter 9: Friction 1 1. 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 2. The interlocking of the depressions and elevations (irregularities) present on the surfaces of the bodies in contact cause friction. Data Insufficient Ambiguous False True None 3. Friction for an object can be reduced by: Lubricating Providing wheels Streamlining All of the above 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 is nothing but the weight of the body Frictional force only exist when there is motion between two objects. Frictional force also exist when there is no motion. None None 6. When two surfaces are coated with a lubricant, then they. Slide upon each other None of these Roll upon each other Stick to each other None 7. Frictional force between two surface in contact is due the Adhesive force between the molecules Both 2 and 3 Cohesive force between the molecules Repulsive forces between the molecules None 8. Tick the most appropriate answer:If you pour some oil onto a floor, the friction would Increase Remain the same Decrease None of these None 9. Select the correct alternative:Friction is increased if An oil is sprayed The surfaces are polished The surface are made wet The surfaces are made dry None 10. 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 Increased friction between the road and the tyres Lubrication of brakes on a wet road None 11. Tick the most appropriate answer:Force of friction comes into play when a/an Object is at rest Object attempts motion Moving object tries to stop All of the these None 12. Which of the following is not an example of force acting at a distance ? Electric force Frictional force Magnetic force Force of gravity None 13. If the outer surface of a glass tumbler is greasy. it would become Difficult to hold it, because friction get reduced Easier to hold it because friction get reduced Difficult to hold it, because friction get increased Easier to hold it because friction get increased None 14. When a ball is left rolling on ground it stops after some time.What bring the rolling ball to rest? Gravitational force Buoyant force Force of friction Air drag None 15. Why are vehicle tires treaded? To decrease grip. To decrease friction. To multiply friction. To increase friction. None 16. Which one of the following can also act as a lubricant in machines? Flow of compressed and purified air. Iron filling Polish on machines Flow of water through the machine None 17. 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. Larger friction with the ice. Smaller friction with the ice. A larger normal force. None 18. 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 19. Galileo did his experiments on inclined planes with smooth surfaces and observed that As smoother the surface, the nearer the ball traveled As rough the surface, the farther the ball traveled None of these As smoother the surface, the farther the ball traveled None 20. 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 causes wear and tear operating in this case is sliding friction resists 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.
