A man weighing $60 k g$ lifts a body of $15 k g$ to the top of a building $10 m$ high in $3 minutes$ . His efficiency is

$10 %$

No worries! We‘ve got your back. Try BYJU‘S free classes today!

$20 %$

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

$30 %$

No worries! We‘ve got your back. Try BYJU‘S free classes today!

$40 %$

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is B
$20 %$

Step 1: Given data and assumption
The mass of the man $= 60 k g$
The mass of the other body $= 15 k g$
Therefore, the mass of the man with the cylinder, $m = 60 k g + 15 k g = 75 k g$ .
Height of the building, $h = 10 m$
Let the acceleration due to gravity be $g$
Step 2: Calculating the efficiency of the man
We know, Energy $= m g h$
The energy required to lift the body of $15 k g$ is $15 g h$
The energy required to lift the mass of the man and the cylinder of $75 k g$ is $75 g h$ .
The efficiency of the man is calculated as,
$\frac{15 g h}{75 g h} \times 100 = 20 %$
The efficiency of the man is $20 %$ .

Hence, option (b) is correct.

Suggest Corrections

Similar questions

(a) Define power. Give the SI unit of power.

(b) A boy weighing 40 kg carries a box weighing 20 kg to the top of a building 15 m high in 25 seconds. Calculate the power. (g = 10 $m / s^{2}$ )

Join BYJU'S Learning Program