# NCERT CLASS IX - Science Textbook Chapter 8 - Motion A stone is thrown in a vertically upward direction with a velocity of5 m s - '1. If the acceleration of the stone during its motion is 10 m s - '2in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?

2
by vishnuOza

• Brainly User
2015-05-14T09:24:08+05:30
I solve this problem by fbd u make an fbd of this
using newtons  equaltion we get
u = 5m/s
v=0
v=u+at'
0=-5  +(-10 t)
t= 0.5 sec
now
v² = u ² +2as
0= 25 - 20s
s=5/4 m
s=1.25 m

2015-05-16T22:46:04+05:30

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U = initial velocity = 5 m/s

a = acceleration = - 10 m/s²        minus because it is in the opposite direction to velocity.

final velocity v will be 0, when the stone reaches the top point before it starts to fall back.

equation of motion:    v² = u² + 2 a s
0 = 5² - 2 * 10 * s

=> s = 25 / 20 = 1.25 meters

time taken to reach the maximum height = t  seconds

we know,    v = u + a t
0 =  5 - 10 * t
t = 5/10 =  0.50 seconds.

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