The Student Room Group
Reply 1
s=ut+1/2at^2
=1/2(-9.8)(2.2^2)
= -23.7m when empty
*speed of sound=300ms^-1
Now:
u=0
s=?
a=-9.8
t=0.8-(s/300)
Now using the same formula:
s=-4.9(0.8-s/300)^2

..And solve this eqn to give s≈-3.13m
Reply 2
C4>O7
s=ut+1/2at^2
=1/2(-9.8)(2.2^2)
= -45m when empty

how did you get this? 1/2(-9.8)(2.2^2) = -23.7m
Reply 3
sorry I was using an awkward calculator..
Reply 4
C4>O7
sorry I was using an awkward calculator..

ok then, thankyou. i thought i was missing something...

the reason i had to ask this question is because i'm only at gcse level, and so have yet to have been taught this method, and am used to having numbers like 9.8 given to me.
Reply 5
ok
do you actually know the motion equations then?
Reply 6
nope.

oh, well, i know some equations, like speed = distance / time:biggrin:

i was puzzled as to what the formula you posted meant. so i just derived how it worked by look at some graphs. oh, i feel clever now.