Question

How much energy is gained by a box of mass 20 kg when a man
(a) carrying the box waits for 5 minutes for a bus?
(b) runs carrying the box with a speed of 3 ms-1 to catch the bus?
(c) raises the box by 0.5 m in order to place it inside the bus?
(g=10 ms^-2)

April 23, 2024

Answer

Mass = 20 kg

(a) As there is no displacement of the man, so work done is Zero.

(b) Work done = Kinetic energy of man

= $1\over 2$ × mass × (velocity)²

= $1\over 2$ × 20 × (3)²

= 90 J

∴ Energy Gained = 90 J

(c) Potential energy = mgh

= 20 × 10 × 0.5 = 100 J

💡 Some Related Questions

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