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NCERT Exemplar Solutions Class 9 Science Solutions for Motion - Exercise in Chapter 8 - Motion

Question 13 Motion - Exercise

A body is thrown vertically upward with velocity u, the greatest height h to which it will rise is,

(a) u/g

(b) u2/2g

(c) u2/g

(d) u/2g

Answer:

Answer is (b) u2/2g

Explanation:

V2= u2+2 as

here v = 0

a = -g

s = H

0 = u² -2gH

H = u²/2g

Video transcript
"welcome to the very another video solution so today's question is a body is thrown vertically upward with the velocity u so here let us consider this ball as a body which is at point a and is having the initial velocity as u the greatest height h to which it will rise we are having the four options over here and the question is asking that it has traveled the greatest height as h and the ball is reaching the point b so what is going to be the value for h so understand one thing when the body is vertically moving upward and is reaching the point b after reaching the point b it will start going downwards so when it reaches a point b it will stop for some time and soon it will stop for some time here the velocity will become zero so initial velocity is u and the final velocity is 0 so here comes the another equation for the motion which is v square equals to u square plus 2 a s now we know that the final velocity that is v square is equals to zero so we will keep the value as zero now let's consider the another velocity which is u square and the initial velocity is u keeping the value u square as it is we will consider 2 now here a is the acceleration due to gravity and we know that the body is going upward that means it is working against the gravity so in order to represent this condition we will use the value of a as minus g which is showing that our body is working against the gravity so putting the value of a as minus g and here s is the height covered here you can see the total height covered by a body is h so we will put the value as h now solving the equation we get u square minus 2 g h and the whole term minus 2 g h will be shifting towards the left hand side and we will get the value as 2 g h equals to u square and h is e equal to u square by 2 g and hence the correct option is b so we can ultimately say that the greatest height that is h is equals to u square by 2g and this is it for this time in order to remain updated keep visiting to lido bye bye"
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