IIT JEE , AIEEE Forum - Physics , Mechanics - A BALL FALLS FROM A HEIGHT ' h ' IN ' t ' SECONDS .THE TIME TAKEN TO COVER LAST METRE IS

BALGANESH

A BALL FALLS FROM A HEIGHT ' h ' IN ' t ' SECONDS .THE TIME TAKEN TO COVER LAST METRE IS ?

aditya_arora04

Hi,

Look,

Distance covered in nth second : u + a(2n-1)/2

here, u=0, n is t a is equal to g

So,

Distance covered : g(2t-1)/2

Also,

h = 0.5gt²

substitute g is h/0.5t²

So, we get :

Distnace covered = (2t-1)h/t²

i hope i am correct, do tell me in case of problems

BALGANESH

no the your ans is not correct

iitkgp_bipin

It would simply be the difference between times taken to cover h meters and h-1 meters.

2h/g -

2(h-1)/g

BALGANESH

but the ans given is 1/GT

rooney

If you know you are correct, forget the book.

spideyunlimited

Time taken to cover (h-1)metres:
h-1 = 1/2 *g * T^2
T = sqrt { 2(h-1) / g }

Also given that it falls through height h in t seconds.
so time taken for the last metre is :
= t - T
= t - sqrt { 2(h-1) / g }
= sqrt {2h / g} - sqrt { 2(h-1) / g }

rabindra8

the time taken to cover last metre is (2h/g)^1/2- {2(h-1)/g}^1/2

^{now details ------- first of all findout the value of total time with the help of u=0 , a=g, y=h, then findout the value of time taken by the ball to cover a distance y=h-1, with the help of u=0, a=g. and finally substract second from first and get your required answer.}

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