Question

A constant force of $35N$ is used to lift a box to a height of $3m$. This takes $15s$ with the help of a small crane. How much minimum power was the crane using?

• A. $7W$
• B. $7kW$
• C. $105W$
• D. $105kW$

Answer 1

The correct option is A

$7W$

Step 1: Given data

Constant force applied is $F=35N$

Height attained by box is $h=3m$

Time taken to lift the box is $t=15s$

Step 2: Finding the minimum power

$$\begin{gathered} Power=\frac{Force\times dis\tan ce}{time} \\ P=\frac{F\times h}{t} \\ P=\frac{35\times 3}{15} \\ P=7W \end{gathered}$$

Thus, the minimum power the crane used is 7 W.

Hence, option (a) is correct.