### 4.1 Video Motion Analysis using “Tracker”

Paste screen captures here with the following graphs for each of the 3 trials:Trial 1

(a) Displacement – time graph

(b) Velocity – time graph

(c) Acceleration – time graph

Trial 2

(a) Displacement – time graph

(b) Velocity – time graph

(c) Acceleration – time graph

### 4.2 Data Analysis

1. Which wheels are your drive wheels? (front or back)
Back wheels

2. What is the circumference of your drive wheels?

37.7cm

3. How far will your car travel in one rotation of the drive wheels?

37.7cm

4. How many rotations (on average ) were there in each run?

7.

5. How much string is used in one rotation of the drive wheels? Show how you calculated this.Length of string used = circumference of the axle

= π*Diameter of axle

= 0.6π

=1.88cm (3sf)

6. The release of the lever is the power stroke. What is the length of your vehicles power stroke?

Length of string released = 22.0 cm

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

Distance that vehicle travels

= (length of power stroke/length of string used in one rotation)*circumference of drive wheels= [(22.0/1.88)*37.7]cm

= 441cm

= 4.41m

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

The distance in #7 (4.41 m) is larger than the one measured (2.1 m). This is due to the air resistance acting on the car and the frictional force between the wheels and the ground which are against the direction of motion. These variables were assumed to be negligible during the calculations.

9. Calculate the average velocity for your car during the period after the spring fully releases.

10. What force causes your car to stop?

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.

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