Ncert – class 8- science – Chapter 9: Friction 1 Welcome to your Ncert - class 8- science - Chapter 9: Friction 1 1. 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 no external force is applied on the ball by the surface Because of frictional force between ball and the ground None 2. If the outer surface of a glass tumbler is greasy. it would become Difficult to hold it, because friction get increased Easier to hold it because friction get reduced Difficult to hold it, because friction get reduced Easier to hold it because friction get increased None 3. 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 resists motion causes wear and tear None 4. 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. A smaller normal force. A larger normal force. Larger friction with the ice. None 5. Tick the most appropriate answer:Force of friction comes into play when a/an Object is at rest Moving object tries to stop Object attempts motion All of the these None 6. 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. 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. None 7. Tick the most appropriate answer:If you pour some oil onto a floor, the friction would Increase None of these Decrease Remain the same None 8. Tick the most appropriate answer:A car skids on a wet or muddy road due to Lubrication of brakes on a wet road Increased friction between the road and the tyres Streamlined shape of the car Reduced friction between the road and the tyres None 9. Why are vehicle tires treaded? To decrease grip. To increase friction. To decrease friction. To multiply friction. None 10. 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 11. Galileo did his experiments on inclined planes with smooth surfaces and observed that As rough the surface, the farther the ball traveled As smoother the surface, the nearer the ball traveled None of these As smoother the surface, the farther the ball traveled None 12. When two surfaces are coated with a lubricant, then they. Stick to each other None of these Slide upon each other Roll upon each other None 13. Which of the following is not an example of force acting at a distance ? Force of gravity Magnetic force Electric force Frictional force None 14. 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 15. Select the correct alternative:Friction is increased if The surface are made wet An oil is sprayed The surfaces are made dry The surfaces are polished None 16. Frictional force between two surface in contact is due the Both 2 and 3 Repulsive forces between the molecules Cohesive force between the molecules Adhesive force between the molecules None 17. When a ball is left rolling on ground it stops after some time.What bring the rolling ball to rest? Gravitational force Force of friction Buoyant force Air drag None 18. Friction for an object can be reduced by: Providing wheels Lubricating Streamlining All of the above None 19. 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 20. The interlocking of the depressions and elevations (irregularities) present on the surfaces of the bodies in contact cause friction. True Data Insufficient False Ambiguous 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.
