| Previous Year Questions of March Examinations from 2010 to 2020 |
| Chapter Name: WORK , ENERGY AND POWER |
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Collision between two particles need not be the physical contact of two particles as in
the case of scattering of the α - particle by a nucleus a) What is the quantity that remains conserved in all types of collisions? b) Suppose an electron and a proton are projected with equal kinetic energy, what will be the ratio of their linear momentums if the proton is 1830 times heavier than an electron? c) The bob of a pendulum released from 30o to the vertical hits on another bob of equal mass at rest. How high does the first bob rise after the collision? (Assume that the collision is elastic and the sizes of the bobs are negligible.) |
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Work is related to force and displacement over which it acts. a) A man tries to pull a rigid wall for a long time but fails to displace it. What is the external work done by him? b) Suggest two conditions for the work done by a force to be zero. c) A body of mass 1 kg travels in a straight line with a velocity v = kx3/2 where k = 5 SI units. Calculate the work done by the net force to displace from x =0 to x = 2 m. |
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Ramesh lifts a body of mass ‘m’ to a height ‘h’ near the surface of the earth in a time ‘t’. a) Draw the force-displacement graph. b) If ‘A’ is the area of the graph, what A / t indicate? |
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According to the work-energy theorem, work done by a force on a body is equal to change in its kinetic energy. a) A lorry and a car moving with a same kinetic energy are stopped by applying breaks which provides the same retardation. Which of them will come to a rest in a shorter distance? Explain. b) If the kinetic energy of a body is doubled, what is the percentage change in its linear momentum? |
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Work is required to be done to lift a body from the ground. Let the body be dropped from the height ‘h’. a) State the work-energy theorem. b) Draw graphically, the variation of K.E and P.E. with the height of the body. Where do you find: i ) The maximum P.E. ? ii) The maximum K.E.? c) State and prove the law of conservation of energy in this case. |
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a) State and explain the work done in the following situations: i) A person carrying a heavy load walks on a level road. ii) A man spending his energy by pushing on a concrete wall. b) A constant force of 200 N displaces a body through 5 m in the direction of the force. Find the work done on the body. |
From the table given
b) How can you find the work done from the above graph? c) Suggest any two situations in which the work done by a force is zero. d) A ball is pushed with a force of 3N for 2s along a frictionless track. The graph shows the force on the body against time. How much work is done by the force? | ||||||||||||
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The scalar product of force and displacement gives work. It can be negative, zero or positive. a) The work done in sliding a load is ......... with respect to frictional force. (zero, positive, negative, infinity) b) State and prove the work energy theorem for constant force. c) A pump on the ground floor of a building can pump water to fill a tank of volume 30 m 3 in 15 minutes. If the tank is 40 m above the ground and the efficiency of the pump is 30%, how munch electric power is consumed by the pump? |
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Several such as billiards, marbles, or caroms involve collisions. a) When two object collide, after collision they could move together, the collision is........ (elastic, completely elastic, inelastic, completely inelastic) b) Show that in a perfectly elastic collision in one dimension, relative velocity after collision is equal to relative velocity before collision c) A ball at rest is dropped from a height of 12 m. It loses 25% of its kinetic energy on striking the ground. Find the height at which it bounces. |
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Force is required to lift a body from the ground to a height ‘h’ and work is measured as the product of force and magnitude of displacement. a) Name the energy possessed by the body at maximum height. Write an equation for it. b) A man of mass 60 kg carries a stone of mass 20 kg to the top of a multi-storeyed building of height 50m. Calculate the total energy spent by him? (9.8m/s2 ) |
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Energy of a body is definad as its capacity of doing work a) The energy possessed by a body by virtue of motion is known as ..................... b) A body of mass 5 kg initially àt rest is s subjected to a horizontal force of 20 N. What is the kinetic energy adquired by the body at the end of 10 s ? c) State whether the following siatement is TRUE of FALSE "The change in kinetic energy of a particle is equal to the work done on it by the net force” |
| A boy throws a ball of mass 200 g with a velocity 20 m/s at an angle of 40° with the horizontal. What is the kinetic energy of the ball at the highest point of the trajectory? |
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Write the work done in each of the following cases as zero, positive or negative a) Work done by centripetal force in circular motion b) Work done by friction c) Work done by gravitational force on a freely falling object d) Work done by the applied force in lifting an object |
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a) If A is perpendicular to B, what is the value of A . B? ( A and B are vectors) b) Find the angle between the force F=(3i + 4j – 5k) N and displacement d= (5i + 4j – 8h) m |
| Write any two properties conservative force |
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Power is the rate is done. at which work a) Express power in terms of force and velocity b) An elevator carrying the maximum load of 1800 kg is moving up with a constant speed of 2 ms-1. The frictional force opposing the motion is 4000 N. Determine the minimum power delivered by the motor to the elevator c) Express your above answer in horse power |
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Find out the sign of work done in the following cases : (a) Work done by a man in lifting a bucket out of a well. (b) Work done by friction on a body sliding down an inclined plane. (c) Work done by an applied force on a body moving on a rough horizontal plane. (d) Work done by the resistive force of air on a vibrating pendulum |
| Graphs of the potential energy, kinetic energy and total energy of an oscillating spring is shown in the figure (a) Find out the potential energy, kinetic energy and total energy from the graph. (b) Derive an expression to find the potential energy of a spring. |
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Write whether the work done in the following cases is positive, negative or zero. (a) The work done by the frictional force during the motion of an object. (b) The work done by the gravitational force during the motion of an object on a horizontal surface. |
| Prove that the mechanical energy of a ball of mass ‘m’ dropped from a height ‘H’ is conserved |
| Calculate the energy used by a 100 watt bulb which is on for 10 hours |