Question

A person weighing 70 kg wt lifts a mass of 30 kg to the roof of a building 10 m high. If he takes 50 second to do so, then the power spent is (g =9.8 m/s2
)

Answer 1

Answer:

• 196 watt is the required answer.

Explanation:

Given:-

• Total mass ,m = 70+30 = 100 kg

• Height ,h = 10 m

• Acceleration due to gravity ,g = 9.8m/s²

• Time taken ,t = 50 s

To Find:-

• Power Spent ,P

Solution:-

As we know that Power is defined as the work done per unit time.

here we have to calculate the power spent by man in against gravity.

• P = mgh/t

Substitute the value we get

→ P = 100×9.8 ×10/50

→ P = 980 × 10/50

→ P = 980/5

→ P = 196 watt.

• Hence, the power spent by the man is 196 watt.

Answer 2

To Find:-

• Find power spent.

Given:-

• The total mass is 70 + 30 = 100kg.
• Person takes in top the roof of the building 10m high.
• Times taken by the person is 50 sec.

Solution:-

$\tt\underline {As \: \: we \: \: know \: \: that:}$

$\tt\implies \: P = \dfrac{mgh}{t}$

Putting values:-

Given,

g = 9.8m/s²

$\tt\implies \: P = \dfrac{100\times 9.8 \times 10}{t}$

$\tt\implies \: P = \dfrac{9800}{50}$

$\tt\implies \: P = 196 watt$

Hence,

• Power spent by man = 196watt.