Question

A 0.5 kg stone takes 4 seconds to reach the ground from a
80 m high building. What is the power of the stone during
the fall? (Take g = 10 N kg-')
(a) 100 W
(b) 160 W
(c) 400 W
(d) 1600 W
​

Answer 1

Answer:

a

Explanation:

power = work done / time

work done here = mgh

m = 0.5kg

g = 10 m/s2

h = 80m

t = 4 sec

mgh = 400 J

power = 400/4

100W

Answer 2

$\huge\mathfrak\red{Answer}$

FIRSTLY I WANT TO GIVE A IMPORTANT INFORMATION FOR TACKLING THE QUESTIONS BASED ON POTENTIAL ENERGY.

THERE ONE THING WHICH MAINLY IGNORED WHILE SOLVING SUCH TYPE OF QUESTIONS. WHICH IS BASICALLY REFERENCE POINT YOU CAN NOT DEFINE POTENTIAL ENERGY WITHOUT YOUR REFERENCE POINT YOU TAKEN.

MY REFERENCE POINT IS SURFACE OF EARTH SO BODY HAS ZERO POTENTIAL ENERGY AT SURFACE OF EARTH AND IF THE SAME BODY RISES WITH HEIGHT h THAN Mgh will BE ITS POTENTIAL DIFFERENCE NOT POTENTIAL ENERGY.

$mass = 0.5kg \\ height = 80m \\ \\ potential \: energy = mgh \\ potential \: energy = 0.5 \times 80 \times 9.8 \\ potential \: energy = 392joules \\ \\ as \: we \: know \: that \: rate \: of \: doing \: \\ work \: is \: known \: as \: power \\ time \: taken = 4sec \\ \\ power = \frac{energy}{time} = \frac{392}{4} = 98joule {sec}^{ - 1} \\ \\ i \: take \: g = 9.8 \: but \: when \: u \: take \\ g = 10 \\ than \: answer \: will \: be \: 100joule {sec}^{ - 1}$