Velocity  Time Graph
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?
37cm
4. How many rotations (on average ) were there in each run?
24.3 rotations
5. How much string is used in one rotation of the drive wheels? Show how you calculated this.
Length of string=28.5cm
Axle circumference=2.98 cm
No. of axle rotations= 28.5/2.98= 9.56
amount if string used per rotation=28.5/9.56=2.98cm
6. The release of the lever is the power stroke. What is the length of your vehicles power stroke? (Length of string released)
28.5cm
7. Calculate how far your vehicle will travel during the power stroke. Show your calculations!!
Since No. of axle rotations= 28.5/2.98= 9.56, Distance travelled=9.56*37=353 cm
8. Compare the answer to #7 to the distance your measured during your car’s power stroke. Discuss possible reasons for different valuables.
The different results may be due to the friction present in the axle to the string and the different ways we coiled the string at the beginning.
9. Calculate the average velocity for your car during the period after the spring fully releases.
Distance travelled after string was released= 900353=547 cm
String took 2s to release, total time after string was released was 6.332=4.33
Average speed= 547/4.33=126 cm/s
10. What force causes your car to stop?The car stops when there is no more resultant force acting on the car.
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?
Assume that the car has no friction,
Let KEnf be the assumed kinetic energy that the car has without friction
Let m = mass of the car = 600g = 0.6kg
Let v = average velocity the car travelled at = 126cm/s = 1.26m/s
KEnf = (1/2)mv^2
KEnf = (1/2)(0.6)(1.26)^2
= 0.47628J
To calculate work done, we first calculate the applied force
Let KEf = work done
Let F be the applied force
Let a = acceleration = 0.1m/s^2
Let d = distance travelled
F = ma
F = 0.6(0.1)
= 0.06N
Then, we calculate work done by using the formula
KEf = F x d
KEf = 0.06(5.47)
= 0.3282J
To calculate work done by the friction,
Let f = Work done by the friction
f = KEnf  KEf
f = 0.47628  0.3282
= 0.14808J
To calculate the frictional force,
Let Ff be the frictional force
Ff = f / d
Ff = 0.14808/5.47
= 0.0271N (3s.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.
This is not a reasonable value. Comparing the maximum kinetic energy, 0.476J(3s.f.), the estimated number has a difference of more than 0.17J. With that difference, it can create a big difference, providing a greater speed towards the car, regardless of the friction that is caused when the string is unwounded. Factors such as the strings roughness would cause the potential energy that is supplied to be converted to other forms such as heat energy and sound energy. Therefore, the estimate would also not be accurate.

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