A Stone Is Thrown Upwards With An Initial Velocity Of 10m/S On The Top Of The Building. The Stone Misses The Building And Fell On The Ground. What Is

A stone is thrown upwards with an initial velocity of 10m/s on the top of the building. The stone misses the building and fell on the ground. What is the height of the building if the total time of flight is 5 seconds?

 

Answer:

Let the height of the building be 'x′m. Let the maximum height attained by the ball when thrown from the building be 'h′m.

Total flight time of ball = 5 sec.

for upward motion

u=−19.6ms1

a=9.8ms2

v=0ms1

We know that, v=u+at

0=−19.6+9.8(t)

19.69.8=t

t=2.

according to equation of kinematics, v2−u2=2ah

0−19.62=2(9.8)h

19.6∗19.62∗9.8=h

h=19.6m

for downward motion

u=0ms−1

a=9.8ms−2

t=3sec since total time is 5 sec and time for upward motion is 2 sec

s=(19.6+x)m

s=ut+12at2

19.6+x=12∗9.8∗32

19.6+x=4.9∗9

x=44.1−19.6

x=24.5m

Therefore height of the building is 24.5 meters.

Explanation: