Question

5. How much power is used by a 40 kg athlete by climbing 10 m high ladder in I0s?​

Answer 1

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392 Watts

${\blue{\huge{\underline{Explanation:}}}}$

This is not an energy question. Since the climb has a time constraint, it asks for power: energy per second.

The energy (same as work) required to lift 40 kg against Earth’s surface gravity 9.8 m/s^2 for distance 10 m is:

force•distance = mass•acceleration•distance

In MKS units that is 40•9.8•10 = 3920 joules. To expend that energy (perform that work) in 10 s requires 3920/10 = 392 watts.

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Answer 2

Given:

Mass of athlete, m = 40 kg

Height of ladder, h = 10 m

Time, t = 10 s

To find:

Power = P

Solution:

Let us find the work done by the athlete

Work done by the athlete to climb the ladder can be given by:

Work, W = mgh (where g is the acceleration due to gravity, here we are taking, g = 10 m/s²)

W = 40 × 10 × 10

W = 4000 Joules

Now, we know

Power = Work done/ Time

P = W/t

P = 4000/10

P = 400

Therefore, Power to be used is equal to 400 J/s or 400 Watts

If you take value of g = 9.8 m/s²

Then,

Power = Work done/ Time

Power = mgh/t

Power = (40 × 9.8 × 10)/ 10

Power = 392 J/s or 392 watts