Question

how much energy is gained by a box of mass 20 kg when a man

1) carrying the box waits for 5 minutes for a bus ?
2) runs carrying the box with a speed of 3
$ms ^{ - 1}$
to catch the bus ?

3) raises the box by 0.5m in order to place it inside the bus ? ( g = 10 m s-2 )


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Answer 1

Answer:

Explanation:1. zero because it is at rest

2.1/2 ×20 ×3×3

=90j

3 mgh =20×10×0.5

=100,j

Or more precisely

Sodium7 Helping Hand

a) no energy gained.

b)no energy gained as muscular energy is converted into kinetic energy.

c) potential energy gained= mgh

= 20 * .5 * 10 joules

= 100 J

Thanks

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Answer 2

Answer:

Given, m = 20 kg

(a) P.E of box = mgh

Here, h is fixed for 5 min

So, gain in energy by box = 0

(b) Man is running with speed = 3 m/s

energy gained by box =

(c) Box is raised by 0.5 m

so, gain in energy = mgh

= 20 × 10 × 0.5

= 100J (With respect to man is bus)