Question

a body projected vertically upwards with a velocity of 10m/s reaches a height of 20 m. if it is projected with a velocity of 20m/s ,then the maximum height reached by a body will be

Answer 1

Final Velocity, V = 0 m/s
Initial Velocity, U = 10m/s
Formula used: V^2 - U^2 = 2AS
where,
A= accelaration
S= distance

-10x10 = 2 x A x 20
A = -100/ 40 = - 5/2 m/s^2

NOW
New Final Velocity, V = 0 m/s
New Initial Velocity, U = 20m/s
A= -5/2 m/s^2
-20x20 = 2 x(-5/2) x S
S = 400/ 5 = 80m

Answer 2

Concept:

If the other features of a body's motion are supplied, kinematics equations can be used to determine an unknown aspect of its motion. If the others are known, kinematics equations can deduce one or more of these variables. These equations describe motion with a constant velocity or acceleration. We can't apply kinematics equations if either the acceleration or the speed is changing since they're only relevant at constant acceleration or constant speed.

Find:

The maximum height reached by the body.

Solution:

Final Velocity, $v=0m/s$

Initial Velocity, $u=10 m/s$

$v^2-u^2=2as\\-10^2=2*a*20\\a=-2.5m/s^2$

Now

New Final Velocity, $v=0m/s$

New Initial Velocity, $u=20 m/s$

$v^2-u^2=2as\\-20^2=2*-2.5*s\\s=80m$

Hence, the maximum height reached by the body is $80m$.

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