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 of frictional force between ball and the ground Because no external force is applied on the ball by the surface Because an object in motion should come to rest no matter what None 2. Friction for an object can be reduced by: Lubricating All of the above Streamlining Providing wheels None 3. 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 4. When a ball is left rolling on ground it stops after some time.What bring the rolling ball to rest? Force of friction Buoyant force Gravitational force Air drag None 5. Tick the most appropriate answer:If you pour some oil onto a floor, the friction would None of these Decrease Remain the same Increase None 6. Galileo did his experiments on inclined planes with smooth surfaces and observed that As smoother the surface, the farther the ball traveled None of these As smoother the surface, the nearer the ball traveled As rough the surface, the farther the ball traveled None 7. 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 resists motion operating in this case is sliding friction None 8. Which of the following is not an example of force acting at a distance ? Electric force Magnetic force Frictional force Force of gravity None 9. 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 10. Why are vehicle tires treaded? To increase friction. To decrease grip. To multiply friction. To decrease friction. None 11. 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 true but statement 2 is false. 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 12. 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 13. Tick the most appropriate answer:Force of friction comes into play when a/an All of the these Object attempts motion Moving object tries to stop Object is at rest None 14. 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. Larger friction with the ice. A larger normal force. None 15. Select the correct alternative:Friction is increased if The surface are made wet An oil is sprayed The surfaces are polished The surfaces are made dry None 16. Which one of the following can also act as a lubricant in machines? Flow of compressed and purified air. Flow of water through the machine Polish on machines Iron filling None 17. Mark the correct statement: None Frictional force also exist when there is no motion. Frictional force is nothing but the weight of the body Frictional force only exist when there is motion between two objects. None 18. If the outer surface of a glass tumbler is greasy. it would become Easier to hold it because friction get reduced Difficult to hold it, because friction get increased Easier to hold it because friction get increased Difficult to hold it, because friction get reduced None 19. In cold weather, we rub our hands to warm them. The force involved in this is: Friction force. Electrostatic force. Gravitational force. Static force. None 20. 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 Reduced friction between the road and the tyres Streamlined shape of the car 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.
