# Homework Help: Distance traveled by projectile

1. Mar 27, 2014

### tristan401

1. The problem statement, all variables and given/known data
Suppose you have a projectile of 120g.
Suppose that projectile is accelerating at 9186.05 m/s/s for 0.129 seconds, to a velocity of 12150 m/s.
Factoring in a 20% drop in Velocity from aerodynamics and friction, it accelerates to roughly 9750 m/s.

What distance did the projectile travel in the 0.129 seconds that it was accelerating? Please provide relevant units of measurement.

2. Relevant equations
d=vt+1/2at2

3. The attempt at a solution
I plugged everything into the above equation, but I don't feel like it is a realistic value, and I'm not sure of what unit is used (m, km, cm, etc...)

2. Mar 27, 2014

### paisiello2

What value did you get?

100g acceleration is huge!

3. Mar 27, 2014

### tristan401

When I plugged everything into the equation, it looked like:
d = (12150)(0.129) + 1/2(94186.05)(0.129)^2
which resulted in 2351.025
I don't know if that's cm or m or km, but thats the number that came out out of the equation

4. Mar 27, 2014

### paisiello2

Try doing it again but this time show all the units explicitly.

5. Mar 27, 2014

### tristan401

d = (12150 m/s) (0.129 s) + 1/2 (94186 m/s/s) (0.129 s)^2

6. Mar 27, 2014

### paisiello2

Ok, can you see which units might cancel with each other?

7. Mar 27, 2014

### tristan401

I don't think I do :(

8. Mar 27, 2014

### paisiello2

Well that's alright. In your equation, what are all the units you are dealing with? Just list them all...

9. Mar 27, 2014

### tristan401

Velocity - m/s
Acceleration - m/s^2
Time - s
distance - ?

10. Mar 27, 2014

### paisiello2

Ok, but each of these can be broken down further into their basic dimensional units also.