A-body-is-projected-vertically-upwards-with-a-speed-of-20m-s-Find-the-time-in-seconds-when-the-body-is-15m-above-it-point-of-projection-g-10m-s-

Question Number 209432 by Tawa11 last updated on 10/Jul/24

A body is projected vertically upwards with

a speed of 20m/s. Find the time in seconds

when the body is 15m above it point of projection.

g= 10m/s²

Answered by A5T last updated on 10/Jul/24

s = u t - \frac{{g t}^{2}}{2} \Rightarrow 15 = 20 t - 5 t^{2} \Rightarrow t^{2} - 4 t + 3 = 0

\Rightarrow t = 3 o r 1

Commented by Tawa11 last updated on 10/Jul/24

Sir, at maximum height, t = 2 \sec .

So, t = 1 \sec is the answer ?

Commented by A5T last updated on 10/Jul/24

A t t = 3; t h e b o d y i s a l s o 15 m a b o v e t h e p o i n t o f

p r o j e c t i o n .

Commented by Tawa11 last updated on 10/Jul/24

Sir, but why at maximum height

t = 2 \sec .

So, the 3 \sec is bigger than the time at maximum

height, can I say t = 1 \sec . only

Commented by A5T last updated on 10/Jul/24

I f w e a r e c o n s i d e r i n g t h e w h o l e m o t i o n, a f t e r

t = 2 t h e b o d y w i l l s t a r t t o d r o p d o w n f r o m 20 m .

Commented by Tawa11 last updated on 10/Jul/24

Thanks sir, I understand

Commented by Tawa11 last updated on 10/Jul/24

sir help me check Q 209430

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