Ncert – class 8- science – Chapter 8: Force and Pressure 1 Welcome to your Ncert - class 8- science - Chapter 8: Force and Pressure 1 1. The non-contact force is : Force due to gravity Force of the friction Tension in string Force of reaction None 2. To move at the same speed, a car with a flat face and another with a streamlined body will require a different amount of force from the engine. The engine of the streamline bodied car will: Exert zero force Exert more force Exert no force Exert less force None 3. Which of the following statement is incorrect: Density of a gas is directly proportional to its pressure at constant temperature. Air is compressible at constant temperature At high altitude air pressure is relatively low At high altitude density of air is relatively high None 4. Which of the following is a contact force: Gravitational force Frictional force Magnetic force Electrostatic force None 5. Change in the state of rest or of uniform motion is brought about by: Acceleration Force Energy None None 6. Write true or false. Correct the false statements. Wooden sleepers are placed under railway tracks in order to increase pres. pressure is independent of the roughness of the surfaces in correct. pressure is inversely proportional to the force applied The perpendicular distance from the pivot of a rotating body to the line of known as the moment arm. None 7. The force between two charge bodies is called muscular force gravitational force magnetic force electrostatic force None 8. It is recommended that the air pressure in motor car tyres be reduced for a motion of the motor cars on sand because deflated tyres cause low pressure on the sand deflated tyres cause high pressure on the sand inflated tyres cause high pressure on the sand inflated tyres cause low pressure on the sand None 9. With the increase in the area of contact of an object the pressure increases none of these decreases is not affected None 10. Which of the following is a correct statement regarding the pressure due to fluids? Force acting on the wall due to pressure is always perpendicular to it because of collision between the molecules takes place oblique to it. Force acting on the wall due to pressure is always oblique to it because of collision between the molecules takes place perpendicular to it. Force acting on the wall due to pressure is always perpendicular to it because of collision between the molecules takes place perpendicular to it. Force acting on the wall due to pressure is always perpendicular to it because of collision between the molecules takes place at any direction to it but its normal reaction on the wall is always perpendicular to it. None 11. Consider two shoulder bags, one with a thin strap, and the other with a wide strap. If both the bags are equally heavy, the bag with the wide strap will be more comfortable to carry because the thin strap has greater inertia per unit length the wide strap enables the weight of the bag to be spread over a bigger area, thus reducing the pressure on the shoulder. the wide strap allows friction to be spread over a bigger area, thus reducing force between shoulder and the strap the thin strap causes greater momentum to be exerted None 12. A vehicle sinks into soft ground. The vehicle is changed so that it does not sink as far. Which change is made? A more powerful engine Wider tyres A lower centre of mass Wheels that are further apart None 13. Which of these is an example of a non-contact force? A toy car slides down the ramp A bar magnet moves a paperclip without touching it A marble rolling on the carpet slows down A child lifts a book lying on the table None 14. Consider the following two cases which involve the motion of an objectCase 1: An apple falling from a tree towards the ground.Case 2: To move a loaded cart on the horizontal ground. Case 2: Involves loaded cart to be moved by pulling force only Case 1: Involves pushing of the apple by earth's gravitational force Case 1: Involves pulling of apple by earth magnetic force Case 2: Involves loaded cart to be moved by both pulling or pushing force None 15. Which of the following statements is /are true Metecors that enter earth atmosphere burn up due to non-contact Contact forces are always observes than non-contact forcs. Magnet force is a non contact force The strength of a non contact force is independet of distance between the bodies. None 16. In the superhit film 'Raja Hindustani', Amir Khan greets his beloved by shaking hand. What kind of force do they exert? Gravitational Weak Electromagnetic Nuclear None 17. When three forces of 50N, 30N and 15N act on a body, then the body is At rest In equilibrium Moving with an acceleration Moving with a uniform velocity None 18. A force is needed to : Keep the body stationary Keep the velocity of body constant Keep the body in motion Change the state of motion or state of rest of the body None 19. A tall vertical cylinder filled with water is kept on a horizontal table top. Two small holes A and B are made on the wall of the cylinder, A near the middle and B just below the free surface of water. There will be no water jet through B Water jet through B will have larger range Water jet through A will have larger range Water jets through A and B will have equal range None 20. Two forces F1 and F2 are acting on a body. F1 is a contact force. F2 is a non - contact force. Then, the body (if at all moving) always moves in direction of None of these F1 Force whose magnitude is greater F2 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.
