# Need Help before a test

1. Aug 28, 2010

### swatmedic05

Acceleration is related to velocity and time by the following expression: A=V^pT^q. Find the powers p and q that make this equation dimensionally consistent. I already got the answer.I guessed and got lucky
Could someone tell me how to get the answer step by step
Please and Thank You

2. Aug 28, 2010

### rock.freak667

Last edited by a moderator: Apr 25, 2017
3. Aug 28, 2010

### swatmedic05

I thought I understood it but I guess i didnt

4. Aug 28, 2010

### rock.freak667

Well post your work up to where you got confused.

5. Aug 28, 2010

### swatmedic05

The exponents from when u posten last time was 2 and -1 where did those come from

6. Aug 28, 2010

### rock.freak667

Ah, remember your rules of indices?

A= L/T2 = LT-2

V=L/T=LT-1

t=T

So you'd have

LT-2= (LT-1)p(T)q

Remember these rules:

(ab)n=anbn and (an)m=amn and that (an)(am)=am+n

It is just applying those rules.

7. Aug 28, 2010

### swatmedic05

whats indices I dont remember that?

8. Aug 28, 2010

### rock.freak667

Last edited by a moderator: Apr 25, 2017
9. Aug 28, 2010

### swatmedic05

so will the answer alway be 1 and -2

10. Aug 28, 2010

### rock.freak667

No you need to simplify the terms on the right side of the equation until you just have one L and one T on the right.

11. Aug 28, 2010

### swatmedic05

I get it now you get the negative by dividing the numbers and subtracting the exponents

12. Aug 28, 2010

### rock.freak667

Well not by subtracting, but by the rule that 1/an=a-n

13. Aug 28, 2010

### swatmedic05

Ok I think I get it now, now i hope he gives us a practice problem before the test

Thank you again

14. Aug 28, 2010

### rock.freak667

You could try this problem and say what you got for 'p' and 'q'.

15. Aug 28, 2010

### swatmedic05

what problem the one I just gave as an example

16. Aug 28, 2010

### rock.freak667

Try S=Aptq

Where S= displacement/distance , A = acceleration and t= time.

17. Aug 28, 2010

### swatmedic05

So is S= [L]

18. Aug 28, 2010

### rock.freak667

Yes.

19. Aug 28, 2010

### swatmedic05

So the equation is:
[L]=[L]/[T]^2*[T]^2

20. Aug 28, 2010

### rock.freak667

Right, now simplify the right side.

EDIT: you forgot the powers 'p' and 'q'

Last edited: Aug 28, 2010