Hi what formula do i use to find for my question

1. Apr 19, 2007

ImsoFly

1. The problem statement, all variables and given/known data
in a final burst of energy near the end of a bike race, Julia accelerates at 0.32 m/s^2 north for 15 s, attaining a final speed of 18.6 m/s south. what was Julia's initial velocity and how far did she travel while accelerating?

3. The attempt at a solution
In this case I think i have to find the V1...but im not sure what the formula I'd use! Any help is appreciated

Last edited: Apr 19, 2007
2. Apr 19, 2007

hage567

You want the equation for acceleration. You've seen it here quite a few times now. Can you try and write it out?

3. Apr 19, 2007

daniel_i_l

What is the most basic formula you know relating the initial and final velocities, the time interval, and acceleration?

4. Apr 19, 2007

ImsoFly

well im saying i need to find v1...i already kno the acceleration formula...its a=delta v/delta t...:uhh:

5. Apr 19, 2007

ImsoFly

Hmm.... is it a=delta v/delta t?

6. Apr 19, 2007

hage567

Yes. So now how do you get v1 out of it? What's delta v mean?

7. Apr 19, 2007

ImsoFly

dleta v means change in velocity:rofl:

8. Apr 19, 2007

hage567

Yes, it does. So what exactly are you having trouble understanding? Why don't you try to find an actual answer to this problem then?

9. Apr 19, 2007

ImsoFly

how am i gonna get the initial velocity??? with a=delta v/delta t??

10. Apr 19, 2007

hage567

You just said that delta v is the change in velocity! So, what does that mean? How would you state that in terms of two velocities?

11. Apr 19, 2007

ImsoFly

i kno v2-v1... but i need to find the initial velocity..mean v1 right?? so how do find v1!

12. Apr 19, 2007

hage567

Rearrange the equation to isolate v1 on one side, and put the numbers in to get a value. Are you having trouble with the algebra?

13. Apr 19, 2007

ImsoFly

yes i am i little bit..

14. Apr 19, 2007

hage567

So you have $$a = \frac{v_2 - v_1}{\Delta t}$$

You want to get the top part (v2-v1) by itself. How would you do that? What would you do get rid of delta t on the right hand side?

15. Apr 19, 2007

ImsoFly

do u know if there's a site that tells you all the formulas like that so i can memorize them?

16. Apr 19, 2007

hage567

You cannot rely on memorizing all the different forms of these equations, it won't work. You must learn to do the algebra.

There might be some examples for you to study here:

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Do you not have a textbook with examples on this kind of thing?

17. Apr 19, 2007

ImsoFly

huh wat is that???

18. Apr 19, 2007

hage567

That website? It's a place to help learn this stuff. It's unlikely you are going to find a website with every equation you want, the way you want it. If you don't like that one, then find another one.

I'm trying to help you with your specific problem, and you have not tried to answer my last question about finding v1. I will help you solve this problem, but you must work with me here.

19. Apr 19, 2007

ImsoFly

do i use Kinematic Equations in grade 10 physics?

20. Apr 19, 2007

hage567

Uh, you're using one right now to solve this question. I don't know what your curriculum is like, but this stuff is usually one of the first things you learn. What else are you going to be learning in this class?