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Displacement formula question

by Voltz
Tags: displacement, formula
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Voltz
#1
Oct7-11, 03:57 PM
P: 21
Hey, first post (:
Was just wondering why the formula for distance is

x = at2

if v = at

and x = vt
then why is it when you substitute in a?

x = distance
v = velocity
t = time
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berkeman
#2
Oct7-11, 04:08 PM
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berkeman's Avatar
P: 40,926
Quote Quote by Voltz View Post
Hey, first post (:
Was just wondering why the formula for distance is

x = at2

if v = at

and x = vt
then why is it when you substitute in a?

x = distance
v = velocity
t = time
Are you familiar with integration and differentiation in calculus? That's the easist way to explain it.
256bits
#3
Oct9-11, 09:09 AM
P: 1,469
Nice post. Very good how you defined the variables

x = vt
means that there is no acceleration so a = 0, and you have to plug into the whole formula and not just part of it.
( ie with a=0 and using only half an equation, x = (1/2) at^2 becomes x = 0 )


The actual forms of the equation are:
x1-x0 = v0 x t with no acceleration ie a=0 Eq 0

With constant acceleration
x1-x0 = ( v0 + v1)/2 x t Eq 1
where ( v0 + v1)/2 is the average velocity

Also v1 = at + v0 Eq 2

sustitute equation 1 into 2
x1 - x0 = ( v0 + at + v0 )/2 x t
or x1 - x0 = v0 t + (1/2) a t^2 Eq 3

the final equation of for rectinear motion with constant acceleration is
(v1)^2 - (v0)^2 = 2a(x1-x0) Eq 4

Hope that helps.
you have to plug into the whole formula - not just part of it.

Voltz
#4
Oct10-11, 05:16 PM
P: 21
Displacement formula question

Thanks good sirs


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