Motion Under Gravity

Question

Sir, i am a student of class 9 and i have a doubt.

The question is.. From the top of a tower of 200m height, a stone is projected vertically upwards with a velocity of 49 m/s.

Calculate the time to reach the ground.

I Did approach the answer through a website .. but i dint understand why the initial velocity (u) was with a negative sign.

Sir.. can u show me the method and the explanations of my doubts,.. Please

Kurma Anudeep · Accepted Answer

let s=200m u=-49m/s a=9.8m/s^2 v^2=u^2+2as =2401+19.6*200 =2401+3920 v=79.5m/s v=u+at 79.5=-49+9.8t 128.5=9.8t t=128.5/9.8=13.11s u is negative because the ball is thrown against the gravitational force ALL THE BEST

General Physics> Motion Under Gravity...

Aditya Pati , 12 Years ago

Kurma Anudeep

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General Physics> Motion Under Gravity...

Aditya Pati , 12 Years ago

Kurma Anudeep

LIVE ONLINE CLASSES

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