Ncert – class 9- science – Chapter 10 – Work and Energy 1 Welcome to your Ncert - class 9- science - Chapter 10 – Work and Energy 1 1. We can explain free-fall of an object on the basis of? Conservation of energy Conservation of potential energy Work-energy theorem Conservation of Kinetic energy None 2. When the force and the displacement are in the opposite directions, the work done by the force is .......... zero negative positive notformthis None 3. When a body falls freely towards the earth, then its total energy: Decreases Increases First increases and then decreases Remains constant None 4. At the start of the free-fall of an object from height ℎ, the potential energy is _____ and kinetic energy is _____. Zero mgh Infinite, mgh mgh, zero mgh, infinite None 5. The height of the water dam in the hydroelectric power station is 20 m. How much water. in 1 second, should fall on turbine, so that 1 MW power is generated ?(g=10m/s^2 ) 500kg 5000kg 7,500kg 10000kg None 6. A body is falling a height ℎ. After it has fallen a height ℎ/2. it will possess only kinetic energy only potential energy half potential energy and half kinetic energy more kinetic and less potential energy None 7. A ball rolling on the ground possesses heat energy potential energy no energy kinetic energy None 8. Work done is equal to? Acceleration Change in kinetic energy None of these Kinetic energy None 9. A ball of mass 2 kg hits a floor with a speed of 4 m/s at an angle of 60ºwith the normal. If (e=1/2); then the change in the kinetic energy of the ball is -6J -12J -3J -9J None 10. Is the work required to be done by an external force on an object on a frictionless, horizontal surface to accelerate it from a speed v to a speed 2v. four times the work required to accelerate the object from 0 to v equal to the work required to accelerate the object from v=0 to v, twice the work required to accelerate the object from v=0 to v three times the work required to accelerate the object from v=0 to v, None 11. The spring will have maximum potential energy when neither (a) nor (b) it is pulled out it is compressed both (a) and (b) None 12. From an automatic gun a man fires 360 bullets per minute with a speed of 360 km/hr. If each bullet weighs 20g, the power of the gun is 300 W 150 W 600 W 75 W None 13. Bullet 2 has twice the mass of bullet 1. Both are fired so that they have the same speed. If the kinetic energy of bullet 1 is K, is the kinetic energy of bullet 2 0.71K 0.25K 0.5K 2K None 14. If a body is released from a certain height, during its fall. Both potential and kinetic energy of that body increase Its kinetic energy increases and potential energy decreases Its potential energy increases and kinetic energy decreases. Both potential and kinetic energy of the body decrease None 15. If water is flowing in a pipe at a height 4m from the ground then its potentialenergy per unit volume is (Reference is taken at ground, g=10m/s 2) $$ 40 \mathrm{kJ} / \mathrm{m}^{3} $$ $$ 20 \mathrm{kJ} / \mathrm{m}^{3} $$ $$ 10 \mathrm{kJ} / \mathrm{m}^{3} $$ $$ 30 \mathrm{kJ} / \mathrm{m}^{3} $$ None 16. A ball is allowed to fall from a height of 10m. if there is 40% loss of energy due is impact then after one impact ball will go up to 8m 6m 10m 4m None 17. Whenever energy gets transformed, the total energy_______. Varies with position Varies with time None of these Remains unchanged None 18. A body is moved along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to $$ t^{2} $$ $$ t^{1 / 2} $$ $$ t^{3/ 4} $$ $$ t^{3/ 2} $$ None 19. A constant force of 5N is applied on a block of mass 20 kg for a distance of 2.0 m, the kinetic energy acquired by the block is 20 J 10 J 15 J 50 J None 20. 9800 joule of energy was spent to raise a mass of 50kg, the mass was raised to a height of 20m none of these 10m 980m 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.
