Question

ꜱᴛᴏɴᴇ ᴅʀᴏᴘᴘᴇᴅ ꜰʀᴏᴍ ʀᴏᴏꜰ ᴏꜰ ʙᴜɪʟᴅɪɴɢ ᴛᴀᴋᴇꜱ 4 ꜱᴇᴄ ᴛᴏ ʀᴇᴀᴄʜ ɢʀᴏᴜɴᴅ . ᴄᴀʟᴄᴜʟᴀᴛᴇ ʜᴇɪɢʜᴛ ᴏꜰ ʙᴜɪʟᴅɪɴɢ !!


ᴋɪɴᴅʟʏ ᴅᴏɴᴛ ꜱᴘᴀᴍ ;)
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Answer 1

Answer:

80 m

Explanation:

for falling from height,initial velocity is 0

g = 10m/s^2

use 3rd law of motion

Answer 2

Answer :

The height of the building is 78.4 m

Explanation :

Given :

A stone dropped from the roof of a building takes 4 s to reach the ground

To find :

The height of the building

Solution :

The second equation of motion,

 $\boxed{\sf S=ut+\dfrac{1}{2}at^2}$

where

S - distance covered

u - initial velocity

t - time taken

a - acceleration

Let "h" m be the height of the building

Here, since the stone is dropped

 u = 0 m/s

 t = 4 sec

 a = g = 9.8 m/s²

 S = 'h' m

Substitute the values,

 $\sf h=0(4)+\dfrac{1}{2}(9.8)(4)^2 \\\\ \sf h=0+4.9 \times 16 \\\\ \sf h=4.9 \times 16 \\\\ \sf h=78.4 \ m$

The height of the building is 78.4 m