Question

A ball is thrown with speed 20 m/s upwards. The ball is above 15m height for duration (g=10m/s2)

Answer 1

!!HOPE IT WILL HELP YOU!!

Answer 2

Given :

Ball is thrown upward with velocity , u = 20 m/s .

Acceleration due to gravity , $g=10\ m/s^2$ .

To Find :

Time taken to reach the height of 15 m .

Solution :

Time can be found by :

$s=ut+\dfrac{at^2}{2}\\\\ut+\dfrac{at^2}{2}=s\\\\20t-5t^2=15\\\\5t^2-20t+15=0\\\\t^2-4t+3=0\\\\t^2-3t-t+3=0\\\\t(t-3)-(t-3)=0\\\\(t-1)(t-3)=0\\\\t=1 , t=3$

Hence , this is the required solution .

Learn More :

Kinematics

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