# Instantaneous velocity expression

1. Sep 20, 2004

### UrbanXrisis

This is an equation of a position v time graph:

x=342t^4-127t^3+1.87t^2+2.45t

I need to use this expression to find the instantaneous velocity at t=0.000s

2. Sep 20, 2004

### arildno

And how is inst. velocity related to position?

3. Sep 20, 2004

### Tom McCurdy

take the derivative of the first equation
then just plug in t
and volla you got instantious velocity

Last edited: Sep 20, 2004
4. Sep 20, 2004

### UrbanXrisis

x`=1368t^3-381t^2+3.74t+2.45

is that correct?

5. Sep 20, 2004

### Tom McCurdy

This is what i got
its in white so you must highlight
$$1368x^3 - 381x^2+3.74X+2.45$$
=2.45=instant velocity

lol
oh t is 0
well this is how you would find instant acceleration at other times
$$4104x^2-762x+3.74$$

sorry I added extra but I am just learning this so I thought it would be good practice.

6. Sep 20, 2004

### Tom McCurdy

Oh sorry I guess tex equations don't turn white

7. Sep 20, 2004

### arildno

Besides, you used x as the variable rather than t

8. Sep 20, 2004

### Tom McCurdy

Darn I was so close to getting it right