where to use v2-U2=2as and s=ut+1/2at2?

Question

in Physics numericals where to use V2-U2=2as and where to use S=ut+1/2at2

Answer 1

Use the first one, in questions where time is not mentioned.Otherwise, it depends on the question, you can use either to find initial speed (u),a and distance(S)

Answer 2

We use v^2 - u^2 = 2as when we are given initial velocity and final velocity and need to know the distance travelled. For example, we are given the initial velocity with which a stone is thrown straight up. We need to know the distance travelled by the stone. We know that final velocity becomes zero. So, we write

0 - u^2 = 2as = -2gh or u^2 = 2gh or h = u/sqrt2g where h is the height, and g is the acceleration due to gravity.

If we have the time and the initial velocity etc. then we use the other equation

s = ut + 1/2 at^2

We also know that v = u + at

And if we substitute that in v^2 - u^2 = 2as and write it as an equation in s, u , a and t, we get s = ut + 1/2 at^2

Answer 3

why are you posting under geography??

this is a physics question that relates to mechanics.

these are variables which have the following meanings:

s = distance
u = initial velocity
t = time
a = acceleration

the equations are correct as follows:

s = u.t + (1/2).a.t^2

v^2 = u^2 +2.a.s

you use these equations to find the unknown variables.
You will require 3 variables at least to solve for the unknown

Answer 4

no, they're of the same accuracy. however when you use a calculator to solve you're problems fractional results are approximated in successive steps hence the apparent miniscule difference in values.there might be fewer approximations in the first equation compared to the second( eg 0.49=~0.5)