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Class XI Physics Work, Energy and Power 4

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Question 1

A particle falls from rest under gravity. Its potential energy with respect to ground (PE) and its kinetic energy (KE) are plotted against time (t). Choose correct graph-

Question 2

A ball loses 15% of its kinetic energy when it bounces back from a concrete floor. When it is thrown vertically downward with a speed v₀ from a certain height h, it bounces back to the same height. Then, if we neglect air resistance, the speed v₀ should be –

Question 3

Hailstone at 0 °C falls from a height of 1 km on an insulating surface converting whole of its kinetic energy into heat. What part of it will melt ?
(Given: g = 10 m/s^2, L_f = 3.3 × 10⁵)

Question 4

A particle is projected at 60º to the horizontal with a kinetic energy K. The kinetic energy at the highest point is

Question 5

A bus of mass 1000 kg has an engine which produces a constant power of 50 kW. If the resistance to motion, assumed constant, is 1000 N. The maximum speed at which the bus can travel on level road and the acceleration when it is travelling at 25 m/s , will respectively be-

Question 6

Power applied to a particle varies with time as P = [3t² – 2t + 1] watts. Where t is time in seconds. Then the change in kinetic energy of particle between time t = 2s to t = 4s is –

Question 7

It is found that the force required to row a boat in a river is proportional to the speed of the boat. When the speed of the boat is kept
v km / hr, the power expended by the boat engine is 24 horse power. What shall be the power (in hp) required, if one wishes to row the boat at a speed 2v km/hr –

Question 8

A 5.0 kg block is thrown up a 30 ° incline with an initial speed v of 6.0 m/s. It is found to travel a distance d = 2.0 m up the plane as its speed gradually decreases to zero. then the loss in mechanical energy of the block due to friction in this process is

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Dec 5JEE & BITSAT