4.1 Video Motion Analysis using “Tracker”

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

(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)

The back wheels.

2. What is the circumference of your drive wheels?

17.3cm (3.s.f)

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

17.3cm (3.s.f)

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

8.69 rotation (3.s.f)

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

Amount of string used = circumference of axle

= 0.2cm x pi

= 0.63cm

6. The release of the lever is the power stroke. What is the length of your vehicles power stroke? (Length of string released)

21cm

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

Distance travelled = (Length of power stroke/amount of string used in one rotation)*circumference of wheels

= 5.77m

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

In our calculation above, the car would travel 5.77m. However, during the testing, it travelled 2m. The calculation above does not include friction, however during the testing, there was not only friction between the wheels and the ground but also in between the axle and the string and the wheels, thus the car did not travel as far.

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

Average velocity = Distance/time

= 2m/3s

= ⅔ m/s

= 0.333m/s (3.s.f)

10. What force causes your car to stop?

The frictional force acting in the direction opposite to the direction of motion increases as the car moves and eventually the magnitude of the frictional force is more than that of the force of the mousetrap and the resultant force is in the opposite direction of motion and the car decelerates to a stop.

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?

Kinetic energy = ½ mv^2

= ½ x (314/100)m x (⅔)^2

= 0.698 Joules (3.s.f)

Work done = 0.698

= 0.698 Joules

= Force x distance

Force of friction = 0.698/2

= 0.349 N (3.s.f)

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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