4. Data Analysis

4.1 Video Motion Analysis using “Tracker”

First trial

Second trial

Third Trial

4.2 Data Analysis

1.     Which wheels are you drive wheels? (front or back)
The back wheels are  our drive wheels

2.     What is the circumference of your drive wheels?
78.5cm (3s.f.)

3.     How far will your car travel in one rotation of the drive wheels?
78.5cm (3s.f.)

4.     How many rotations (on average ) were there in each run?
14.4 rotations (3s.f.)
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5.     How much string is used in one rotation of the drive wheels? Show how you calculated this.
Length of string / No. of rotations = Length of string used in one rotation
64 cm          /         14.4           =                           4.44cm (3s.f.)

6.     The release of the lever is the power stroke. What is the length of your vehicles power stroke? (Length of string released)
64cm - 3cm = 61cm

7.     Calculate how far your vehicle will travel during the power stroke. Show your calculations!!

8.     Compare the answer to #7 to the distance your measured during your car’s power stroke. Discuss possible reasons for different valuables.

9.     Calculate the average velocity for your car during the period after the spring fully releases.
(Total Distance travelled - Distance travelled while string is releasing) /  ( Total Time taken - Time taken for string to fully release) = Average velocity (Run 1)
(Repeat 3 times with the results from different runs)

(Average velocity (Run 1) + Average velocity (Run 2) + Average velocity (Run 3)) / 3 = Average velocity (Average of all)

(11.0 - 5.0) / (8.0 - 2.0) = 1.00m/s
(12.0 - 4.0) / (7.0 - 1.0) = 1.33m/s (3s.f.)
(11.0 - 4.0) / (7.0 - 2.0) = 1.40mls

(1.00 + 1.33 + 1.40) / 3 = 1.24m/s (3s.f.)

10.   What force causes your car to stop?
The forces that cause our car to stop is air resistance and friction

11.   The work done by a force is calculated by multiplying the force times the distance over which it acts. The work done on an object is equal to the change in its kinetic energy. Can you find a way to calculate the force of friction? Use equations and explain your steps. HINT: Be careful, you have calculated average velocity. How can you find the total amount of kinetic energy (immediately after spring release) if we assume the acceleration during coasting was constant?
12.   Various experiments have been done to measure the potential energy available from the spring. One estimate is 0.65 Joules. Using your estimates of the maximum kinetic energy of your car and the work done by friction, discuss whether or not this is a reasonable value. Can you account for any differences in the forms of energy? You must justify all of your arguments.