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 is nothing but the weight of the body Frictional force also exist when there is no motion. None 2. A ball moving on ground eventually stops. Mark the correct reason Because of frictional force between ball and the ground Because an object in motion should come to rest no matter what None of these Because no external force is applied on the ball by the surface None 3. Which of the following is not an example of force acting at a distance ? Frictional force Force of gravity Magnetic force Electric force None 4. In cold weather, we rub our hands to warm them. The force involved in this is: Friction force. Static force. Electrostatic force. Gravitational force. None 5. Frictional force between two surface in contact is due the Repulsive forces between the molecules Both 2 and 3 Adhesive force between the molecules Cohesive force between the molecules None 6. Tick the most appropriate answer:A car skids on a wet or muddy road due to Reduced friction between the road and the tyres Lubrication of brakes on a wet road Streamlined shape of the car Increased friction between the road and the tyres None 7. Friction for an object can be reduced by: Streamlining All of the above Lubricating Providing wheels None 8. When two surfaces are coated with a lubricant, then they. Slide upon each other None of these Stick to each other Roll upon each other None 9. 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 10. Tick the most appropriate answer:Force of friction comes into play when a/an Object attempts motion Object is at rest Moving object tries to stop All of the these None 11. 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 depends on the nature of the material resists motion causes wear and tear None 12. Tick the most appropriate answer:If you pour some oil onto a floor, the friction would None of these Decrease Increase Remain the same None 13. Why are vehicle tires treaded? To decrease grip. To decrease friction. To increase friction. To multiply friction. None 14. 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 not the correct explanation of statement 1. Statement 1 is false but statement 2 is true. 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 15. 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 16. 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 As rough the surface, the farther the ball traveled None of these None 17. Select the correct alternative:Friction is increased if The surfaces are polished An oil is sprayed The surface are made wet The surfaces are made dry None 18. 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. Smaller friction with the ice. A larger normal force. Larger friction with the ice. None 19. 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 20. 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 increased Easier to hold it because friction get reduced Difficult to hold it, because friction get increased 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.
