Question

A boy of mass 50 kg runs
up a staircase of 45 steps in 9 s. If the
height of each step is 15 cm, find his
power. Take g = 10 m s-2.​

Answer 1

$\huge\sf\underline{\red{Answer}}$

Given mass of body (m)=50kg

h=45×15=675cm=6.75m

t=9s

δ=10m

Potential energy =mgh

=(50×10×6.75)5

=33755

Power of the body = Potential energy/time

= 3375/9

=375W

$\huge\sf\underline{\pink{Thanks}}$

Answer 2

❄️ Given :

• Total mass of the boy = 50 kg
• He runs up 45 steps in 9 s
• Height of each step = 15 cm
• Find his power.
• Take g = 10 m s^-2

❄️ Solution :

Weight of the boy,

mg = 50 kg × 10 m s^-2 = 500 N

Height of the staircase,

h = 45 × 15/100 m = 6.75 m

Time taken to climb, t = 9 s

From Eq. (11.8),

$\bf power, ~\pink{P = \dfrac{ Work \: \: done }{time \: \: taken} } \\ \\ \twoheadrightarrow \: \bf\frac{mgh}{t} \\ \\ \twoheadrightarrow \bf \: \frac{500 \:N \: \times 6.75 \: m}{9 \: s} \\ \\ \twoheadrightarrow \pink{\bf \: 375 \: W.} \\ \\ \\ \: \: \: \: \: \large{ \pink{\underline{\underline{\boxed{ \boxed { \rm \purple{ Power~~is~~375~W.}}}}}}}$