Ncert – class 8- science – Chapter 9: Friction 1 Welcome to your Ncert - class 8- science - Chapter 9: Friction 1 1. Galileo did his experiments on inclined planes with smooth surfaces and observed that As smoother the surface, the nearer the ball traveled None of these As smoother the surface, the farther the ball traveled As rough the surface, the farther the ball traveled None 2. Mark the correct statement: Frictional force only exist when there is motion between two objects. Frictional force is nothing but the weight of the body Frictional force also exist when there is no motion. None None 3. Brakes of a very small contact area are not used, although friction is independent of area. It is because friction: causes wear and tear operating in this case is sliding friction resists motion depends on the nature of the material None 4. Tick the most appropriate answer: If you pour some oil onto a floor, the friction would Increase Decrease Remain the same None of these None 5. In cold weather, we rub our hands to warm them. The force involved in this is: Static force. Electrostatic force. Friction force. Gravitational force. None 6. 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 7. 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 8. When two surfaces are coated with a lubricant, then they. None of these Stick to each other Slide upon each other Roll upon each other None 9. When a ball is left rolling on ground it stops after some time.What bring the rolling ball to rest? Buoyant force Gravitational force Air drag Force of friction None 10. Which of the following is not an example of force acting at a distance ? Magnetic force Frictional force Force of gravity Electric force None 11. A ball moving on ground eventually stops. Mark the correct reason Because of frictional force between ball and the ground Because no external force is applied on the ball by the surface None of these Because an object in motion should come to rest no matter what None 12. Select the correct alternative: Friction is increased if The surfaces are made dry An oil is sprayed The surface are made wet The surfaces are polished None 13. Tick the most appropriate answer: A car skids on a wet or muddy road due to Streamlined shape of the car Increased friction between the road and the tyres Reduced friction between the road and the tyres Lubrication of brakes on a wet road None 14. 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 15. Why are vehicle tires treaded? To decrease friction. To multiply friction. To decrease grip. To increase friction. None 16. Frictional force between two surface in contact is due the Adhesive force between the molecules Both 2 and 3 Repulsive forces between the molecules Cohesive force between the molecules None 17. Friction for an object can be reduced by: Providing wheels Lubricating Streamlining All of the above None 18. 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 19. The interlocking of the depressions and elevations (irregularities) present on the surfaces of the bodies in contact cause friction. True False Data Insufficient Ambiguous None 20. 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 smaller normal force. A larger normal force. 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 comment Enter your email address to comment Enter your website URL (optional) Save my name, email, and website in this browser for the next time I comment.
