Simple velocity/motion question

[stuarthin]

I'm having some problem with a few results I gathered from a series of tests and am afraid I am missing something and/or misunderstanding some basic concepts.

My method for this test was to run a dynamics trolley down a slope at different angles, each angle being an amount of books starting from 3 books (Test 1) and ending with 7 books (Test 5).

My problem is, why are my results so...unexpected? Basically the higher the books, the greater the velocity right? Here are my peak velocities for the 5 tests:

T1 : 59cm/s
T2 : 94cm/s
T3 : 106cm/s
T4 : 87.5 cm/s
T5 : 102cm/s

Stopping distances:

T1 : 18.5 cm
T2 : 55 cm
T3 : 65 cm
T4 : 41 cm
T5 : 59 cm

The aim of this experiment is to determine whether or not speed is related to the stopping distance of a car. I intended to explain this statement throughout a series of test determining the speed, distance, and acceleration of a dynamics trolley and using data provided to solve the investigation.

Independent variable : Speed of Trolley
Dependent variable: Distance (stopping)


My attempt at solution: Possibly where the trolley stopped at the end of each test. I'm really not sure and was hoping somebody would point out the answer for me. I'm completely stumped as to why the peak velocity does not go higher and instead sort of jumps around.

 

[Leong]

Perhaps you should consider the air resistance (the drag force) and the friction to come out with a reasonable explanation that is consistent with your data.