# Hi what formula do i use to find for my question

## Homework Statement

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?

## 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

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hage567
Homework Helper
You want the equation for acceleration. You've seen it here quite a few times now. Can you try and write it out?

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

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

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

What is the most basic formula you know relating the initial and final velocities, the time interval, and acceleration?
Hmm.... is it a=delta v/delta t?

hage567
Homework Helper
Hmm.... is it a=delta v/delta t?

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

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

dleta v means change in velocity:rofl:

hage567
Homework Helper
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?

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?

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

hage567
Homework Helper
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?

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?

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

hage567
Homework Helper
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?

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?

yes i am i little bit..

hage567
Homework Helper
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?

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?

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

hage567
Homework Helper
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?

huh wat is that???

hage567
Homework Helper
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.

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.

do i use Kinematic Equations in grade 10 physics?

hage567
Homework Helper
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?

chroot
Staff Emeritus
Gold Member
ImsoFly, it really appears to me that you are desperately trying to avoid actually learning anything. It seems as though you just want to memorize a huge list of formulas, and then just pick the right one for each problem.

This might get you through your first year of physics education, but it will completely prevent you from ever understanding (or succeeding in) any later classes.

Besides, you're looking at this the wrong way. You have two options:

(1) Memorize a huge list of formulas, which will take you forever and will likely result in many errors.

(2) Memorize a very small list of relationships, and use algebra to rearrange those relationships in any way you need them, in a matter of seconds.

Hint: Option (1) won't get you anywhere. Quit resisting option (2).

- Warren

hage567
Homework Helper
Well said, chroot.

ImsoFly, if you are struggling with the algebra, perhaps some extra tutoring from your teacher would be beneficial. Once you have the basics down (it won't take long), you will be all set. It just takes lots of practice and some patience.