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

*After modification

**Trial 1**Displacement Time

Velocity Time

Acceleration Time

**Trial 2**Displacement Time

Velocity Time

Acceleration Time

4.2 Data Analysis

1. Which wheels are you 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?

18

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

1. Which wheels are you 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?

18

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

0.942cm

circumference of axle= πxd

= πx3

= 9.42mm (3sf)

= 0.942cm

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

(Length of string released)

44.6cm

(44.6/0.942)x37.7=1780cm (3sf)

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 measured was much lesser. This

is most probably due to air resistance and friction between the wheels and the floor as it was

neglected during the calculations.

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

v=((7.25m/5.5s-3s)+(6m/6s-2.1s)+(7.25/(6.5-2.4))/3

=2.07m/s (3 s.f.)

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?

Mass of car = 320 g = 0.32kg

estimate highest velocity = 3 m s^-1

Find highest KE = ½m v^2 (½ x 0.32 x 3^2 = 1.44 J)

highest KE = work done by the spring = force exerted by the spring =1.44

resultant force can be found in F=ma, mass of car times acceleration

estimate acceleration = 1 ms^-2

0.32 x 1 = 0.32

frictional force = force exerted by spring - resultant force (1.44 - 0.32 = 1.12N)

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.

No, for the question before, I calculated and estimated the potential energy stored to be 1.44J,

and some energy was already lost due to some friction. The opposing friction would be higher

than the force exerted by the spring, thus the car would not move if the spring stored 0.65 J.

Energy may be converted to heat, friction, sound and kinetic energy.

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