Ncert – class 8- science – Chapter 9: Friction 1 Welcome to your Ncert - class 8- science - Chapter 9: Friction 1 1. Which of the following is not an example of force acting at a distance ? Electric force Force of gravity Frictional force Magnetic force None 2. Which one of the following can also act as a lubricant in machines? Iron filling Flow of compressed and purified air. Flow of water through the machine Polish on machines None 3. Galileo did his experiments on inclined planes with smooth surfaces and observed that None of these As smoother the surface, the farther the ball traveled As smoother the surface, the nearer the ball traveled As rough the surface, the farther the ball traveled None 4. 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 of frictional force between ball and the ground Because no external force is applied on the ball by the surface None 5. Why are vehicle tires treaded? To increase friction. To multiply friction. To decrease grip. To decrease friction. None 6. The interlocking of the depressions and elevations (irregularities) present on the surfaces of the bodies in contact cause friction. True Ambiguous Data Insufficient False None 7. Frictional force between two surface in contact is due the Repulsive forces between the molecules Adhesive force between the molecules Cohesive force between the molecules Both 2 and 3 None 8. 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 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. Both statements 1 and 2 are true and statement 2 is not the correct explanation of statement 1. None 9. When two surfaces are coated with a lubricant, then they. Roll upon each other None of these Slide upon each other Stick to each other None 10. 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 11. When a ball is left rolling on ground it stops after some time.What bring the rolling ball to rest? Gravitational force Air drag Force of friction Buoyant force None 12. Select the correct alternative:Friction is increased if The surfaces are polished The surface are made wet An oil is sprayed The surfaces are made dry None 13. If the outer surface of a glass tumbler is greasy. it would become Easier to hold it because friction get increased Easier to hold it because friction get reduced Difficult to hold it, because friction get increased Difficult to hold it, because friction get reduced None 14. In cold weather, we rub our hands to warm them. The force involved in this is: Friction force. Gravitational force. Static force. Electrostatic force. None 15. 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 resists motion operating in this case is sliding friction causes wear and tear None 16. 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 17. 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 18. 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 Lubrication of brakes on a wet road Reduced friction between the road and the tyres None 19. Friction for an object can be reduced by: All of the above Providing wheels Streamlining Lubricating None 20. Mark the correct statement: Frictional force only exist when there is motion between two objects. Frictional force also exist when there is no motion. None Frictional force is nothing but the weight of the body 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.
