Question

A boy weighing 35 kg carries a bag of 15 kg climbs stairs in 5 s f 15 cm height. Calculate the power of the boy. take g=10​

Answer 1

Given:-

Weight of boy = 35 kg

Weight of bag = 15 kg

Height he covered = 15 cm or 0.15 m

Total time taken = 5 second

Acceleration due to gravity (g) = 10 m/s²

Solution:-

Total weight carried upward = ( weight of boy + weight of bag )

                                               = 35 kg + 15 kg

                                               = 50 kg

The Force applied by the boy = Mass × Acceleration due to gravity (g)

                                                 ⇒ 50 kg × 10 m/s²

                                                 ⇒ 500 Newton

Potential energy of the boy = Force × Displacement

                                             ⇒ 500 N × 0.15 m

                                             ⇒ 75 Joule

We know that,

Work-Done = Energy ( Potential energy )

Work-Done = 75 Joule

Power = $\frac{Work-Done}{Time}$

          ⇒ $\frac{75 J}{5 s}$

          ⇒ 15 Watt

∴ The Power of boy is equal to 15 Watt.

Some Important Terms:-

• Work-Done = Force × Displacement × Cosθ    [ where, Cosθ = Angle between Force applied and Displacement of the Body ]

• Power = $\frac{Work-Done}{Time}$

• Energy is of two types:-

1. Kinetic Energy = $\frac{1}{2}$ × Mass × Velocity²
2. Potential Energy = Mass × Acceleration Due to Gravity (g) × Height