Why does the velocity fluctuate before gradually slowing down?

[deaninator]

Homework Statement

Ok my group and I did an experiment relating to shake and go cars. I made an hypothesis that as time (seconds) goes on, then the car's velocity would go up gradually and then would slow down gradually. However though our data proved that as the time goes by, the velocity of the car doesn't simply go up. For example at 4.3 sec the velocity was 0.709 m/s. Then at 4.33 seconds the velocity was 0.714 m/s but at 4.4 sec the velocity was 0.696 m/s. And at 4.433 sec the velocity was 0.729. Why does the velocity fluctuate before gradually slowing down and how can I prove this?

Homework Equations

The shake and go car we used:
http://www.fisher-price.com/fp.aspx?st=4040&e=shakengoproduct&pcat=shakengo_racers&pid=32741

The Attempt at a Solution

 

[thrill3rnit3]

How are you calculating these velocities?

 

[deaninator]

How are you calculating these velocities?

A motion detector.

 

[thrill3rnit3]

There are several possible explanations. Did the surface that the can ran on have equal roughness? Maybe the motor wasn't producing consistent power (I'm using the term "power" loosely here)?

The conditions certainly weren't ideal so you can't pinpoint with absolute uncertainty as to why the velocity fluctuates. Plus the velocities seem pretty close to each other (within a given range).

 

[deaninator]

There are several possible explanations. Did the surface that the can ran on have equal roughness? Maybe the motor wasn't producing consistent power (I'm using the term "power" loosely here)?

The conditions certainly weren't ideal so you can't pinpoint with absolute uncertainty as to why the velocity fluctuates. Plus the velocities seem pretty close to each other (within a given range).

Well yeah I don't have to be exact, I just some reasonable reasons why i did fluctuate. Now I just need to prove these reasons.