Finding constant acceleration, unit difficulty

Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
2 replies · 2K views
PhysicallyAbel
Messages
26
Reaction score
1

Homework Statement


An Indy 500 race car's velocity increases from 4m/s to 36m/s over a 4 second time interval. What is its acceleration? 4m/s is the initial velocity, 36 m/s is the final velocity, and time is 4 seconds.

Homework Equations


final velocity = initial velocity + (acceleration x time)[/B]

The Attempt at a Solution


36m/s = 4m/s + a(4s)
32m/s = a(4s)
a = 8?[/B]

Here's my problem. I know how to work out the equation and solve for acceleration. However, when you divide 32m/s by 4 seconds, I thought that you canceled the units. Which means you would be left with 8 meters (because seconds cancel out). However, I'm aware the correct answer is 8m/s^2 because acceleration is always squared.

Can someone explain my fundamental misunderstanding? It's so simple, but It's really confusing me.
 
Physics news on Phys.org
You cannot cancel the units, both time units are in the denominator:

1 m/s / (1 s) = 1 ((m/s)/s) = 1 m/s^2

just as (1/2)/2 = 1/4 and not (1/2)/2 = 1.
 
Orodruin said:
You cannot cancel the units, both time units are in the denominator:

1 m/s / (1 s) = 1 ((m/s)/s) = 1 m/s^2

just as (1/2)/2 = 1/4 and not (1/2)/2 = 1.

Thank you so much, I knew I was making an elementary mistake. I'm an idiot.