What is the correct formula for calculating velocity?

[whitestrat69]

ok just say you have these values:

s=1.3m
u=0ms
v=?
a=10
t=0.5099

Now these values represent the vertical part of a vector..

now to work out velocity it uses a formula, v=s/t, = 1.3/0.5099 = 2.55ms... which is incorrect.. .

but using this formula.. v^2=u^2 + 2as
Plug in all the values
v= 5.1ms

why does this occur? is the velocity formula (s/t) only used when an object is in linear motion??

 

[learningphysics]

v = s/t is only for constant velocity motion... ie when acceleration = 0.

for accelerated motion, you can say average velocity is s/t... but your question is asking for v which is final velocity...

you will notice that:

average velocity = (u + v)/2

s/t = (u+v)/2

2.55m/s = (0 + v)/2

gives v = 5.1m/s.

so you can think of it like that. But I recommend to only think of v = s/t for constant velocity motion...

 

[whitestrat69]

thankyou again!