Mousetrap Car Physics –

Science 10

Mr. James

Mousetrap Cars – Table of Contents

Day Activity

1 Explain Project, Research

2 Finish Research

3 Design Car

4 Build

5 Build

6 Build

7 Test

8 Test

9 Distance and Displacement

10 Potential Energy

11 Kinetic Energy

12 Work

13 Speed and Velocity

14 Acceleration

15 Analysis

16 Analysis

17 Review

18 Review

19 Unit Test

20 Race Day!

Mousetrap Cars – Day 1

Guiding Question: How can a mousetrap car help us better understand the physics at work in the world around us? Introduction: Your task is to build an originally designed vehicle powered by a mousetrap to run along a course, which will be five meters long (minimum). Your car will be designed to compete in one of three categories below. Each category requires specific parts of the build to be customized, so be sure you start your build with the end goal in mind. A very popular method of propulsion is to tie one end of a string to the arm (or an extended lever arm) on the mousetrap and the other end to the axle. By winding the string around the axle, the mousetrap's spring, when released, pulls on the string causing the wheels to turn and thus making the car move (however, other creative ways to convey power from the mousetrap to the car can be used). There will be team entries in the following events:

★ SPEED: Fastest car to finish wins. To be run in heats of three cars.

★ DISTANCE: This is the most popular and the easiest to judge. The car that travels

the longest linear distance on one swing of the mousetrap lever wins.

★ MOST POWERFUL: The car must be able to pull a small trailer loaded with

weights. The car moving the greatest weight for a designated distance is the win.

Key Concepts: a) Design a mousetrap car that will travel a maximum speed/acceleration over a 5 meter race. b) Demonstrate an understanding of the physics principles incorporated in your design (in a report). The project consists of 5 phases: Mousetrap Car Design

Procurement of parts - Pass CHECKPOINT 1

Mousetrap Car Construction - Pass CHECKPOINT 2

Mousetrap Car Performance Evaluation - Race day.

Mousetrap Car Physics Analysis (Report)

Research - Day 2 As with any good project, you must first research to develop necessary background information before you get started. Use the following websites to answer questions 1-5 below:

• http://www.docfizzix.com/topics/science-concepts/MouseTrap-Vehicles/

• http://www.docfizzix.com/topics/construction-tips/Mouse-Trap-Cars/adjusting-pulling-- force.shtml

• http://www.docfizzix.com/topics/design-basics/MouseTrap-Cars/mousetrap-racers-friction.shtml

• http://www.drivingscience.org/mousetrap-car-resources.html

• http://www.real-world-physics-problems.com/mousetrap-car-physics.html Questions: 1. Explain the force that allows the mousetrap car to move: ____________________________________________________________________________________________________________________________________________ 2. What forces acting on the mousetrap car are decreasing its momentum? Be specific. ____________________________________________________________________________________________________________________________________________ 3. What can you do to decrease the forces acting on the car? ____________________________________________________________________________________________________________________________________________ 4. Draw and label the parts of any example of a mousetrap car below: Wheels, drive axle, lever arm, chassis (body), mousetrap

5. List at least two items that could be used for each of the following parts:

a. Wheels: ___________________________________________________________

b. Axle: _____________________________________________________________

c. Body: _____________________________________________________________

6. http://www.docfizzix.com/topics/design-basics/MouseTrap-Cars/mousetrap-propulsion.shtml a. How does a mousetrap car work? ______________________________________________________________________ b. How is the string connected to the axle? ______________________________________________________________________ 7. http://www.docfizzix.com/topics/construction-tips/Mouse-Trap-Cars/adjusting-pulling-force.shtml a. Where should you place the mousetrap on the chassis for the best performance for speed? ______________________________________________________________________ b. if you are building a mousetrap vehicle for distance? ______________________________________________________________________ 8. http://www.docfizzix.com/topics/construction-tips/Mouse-Trap-Cars/adjusting-pulling-force.shtml a. How long should you make your vehicle’s lever arm for best performance if you want speed/power? ______________________________________________________________________ b. If you are building a mousetrap vehicle for distance? ______________________________________________________________________ 9. What should you do if your mousetrap car suddenly stops or slows down to fix it? http://www.docfizzix.com/topics/design-basics/MouseTrap-Cars/mousetrap-racers-friction.shtml

____________________________________________________________________________________________________________________________________________

10. What do you do if your axle slides back and forth (wheels to rub against the chassis which slows/stops the car)? http://www.docfizzix.com/topics/design-basics/MouseTrap-Cars/mousetrap-racers-friction.shtml

______________________________________________________________________

11. How can you make your vehicle go further? (4 ways) http://www.docfizzix.com/topics/design-basics/MouseTrap-Cars/mousetrap-distance-basics.shtml

1.____________________________________________________________________ 2.____________________________________________________________________ 3.____________________________________________________________________ 4. ___________________________________________________________________ 12. When designing a trap car what are the 2 variables that truly determine performance? How can you minimize the one that slows you down? http://www.docfizzix.com/topics/design-basics/MouseTrap-Cars/mousetrap-distance-basics.shtml

2 variables:__________________________________________________________ How do you minimize one: ______________________________________________________________________ 13. What are the 4 major differences between the speed car design and the distance car design? http://www.docfizzix.com/topics/records/Mouse-Trap-Vehicles/

a. ________________________________________________________________________________________________________________________________

b. ___________________________________________________________________

_____________________________________________________________

c. ________________________________________________________________________________________________________________________________

d. ___________________________________________________________________

_____________________________________________________________ 14. Restate each of Newton’s Laws of Motion and then explain how the law would apply to mousetrap powered vehicles. http://www.docfizzix.com/topics/science-concepts/MouseTrap-Vehicles/newtons-laws.shtml

Law One: _____________________________________________________________________ How does it apply? Law Two: _____________________________________________________________________ How does it apply? Law Three: _____________________________________________________________________ How does it apply? 15. How do you make a good distance trap car? List 3 ways. http://www.docfizzix.com/topics/design-basics/MouseTrap-Cars/mousetrap-distance-basics.shtml

a. ________________________________________________________________

b. ________________________________________________________________

c. ________________________________________________________________

Mousetrap Car Planning Sheet – Day 3

Make 2 small sketches of possible designs for your mousetrap car. Include how many wheels you will use and label what you will use for each part of the mousetrap car (see Question #4 if you need to remember the parts). You will need to:

1. Draw the car using a top view/side view. 2. Label all parts of the car including materials used for each part 3. Include measurements (to scale if you are able)

INITIAL DESIGN

Approved By Mr James: __________________________

Calculating Distance and Displacement – Day 9 Questions: 1. Define the term distance

______________________________________________________________________________________________________________________________________

2. Define the term displacement ______________________________________________________________________________________________________________________________________

3. What is the difference between the two terms? ______________________________________________________________________________________________________________________________________

4. The shortest distance between two points is found using a ______________ line. This is an example of ___________________. In this activity you are going to find the displacement and distance your car travels in order to determine if you need to make any changes to the alignment of your wheels.

Procedure: Use the diagram below to help answer the following questions:

Diagram/Calculations for Displacement and Distance

1. Set out a piece of string (AB) ____ meters long. Make sure this string is straight and

put a piece of tape at both ends to hold it in place. 2. Take a second piece of string (BC) and tape it at one end (B), but do not string it out.

This is the point where your car will start. 3. Place your car down at point B. 4. Run your car. Did it follow the straight string? If not, string the second piece of string

in the direction your car was travelling. 5. Measure the distance your car travelled using a ruler/meter stick. 6. Now using Pythagorean Theorem, determine the length of line AC to find out how

much extra your car has travelled compared to the displacement.

Conclusion:

1. What was the displacement your car should have travelled if it went straight? (Remember to include direction if this is a vector quantity)

______________________________________________________________________________________________________________________________________________

2. What was the distance your car ACTUALLY travelled? ______________________________________________________________________________________________________________________________________________

B

A

C AB = _________ BC = _________ Formula/Calculations for AC; AC = _________

3. How much extra distance did your car travel compared to the shortest displacement it could have travelled.

______________________________________________________________________________________________________________________________________________ 4. Is this an acceptable? Are you going to make any changes to your car in order to

decrease the distance it travels in the wrong direction? If, so describe the changes below, so you will remember to put them in your analysis at the end!

________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Measuring Potential Energy – Day 10

We now know how much kinetic energy we got from our mousetrap car. But to work out the efficiency we need to know how much stored energy was available in the mousetrap.

The Energy stored in a spring can be found by the following equation:

E potential = potential energy stored in the spring (Joules)

F = the force the spring produces in Newtons (N) d = the distance over which the force acts in metres (m)

To do this we need to know how much Force the arm on the mousetrap produces.

Potential Energy Experiment Results

6) Use the Newton Gauge to measure the Force produced by the spring. You may find that the Force is not the same as you pull the spring back from the start to the full extension. Record your results in the space below.

Fill out the table to record the Force recorded at various angles:

Angle (°) Force (N)

Average Force Applied:

Now that we know the average force that is applied we need to determine over what distance that force acts. This can be found by calculated how far the end of the mousetrap “hammer” moves. The end of the hammer traces out part of a circle. The radius of the circle is equal to the length of the hammer.

7) Calculate the distance travelled using the equation for the circumference of a circle.

8) The energy stored in the spring is equal to the Average Force multiplied by the Distance over which the force acts. Calculate the energy available from your car and record it in the space below.

9) The efficiency of your mousetrap car is given by the Kinetic Energy divided by the Potential Energy multiplied by 100. Calculate the efficiency of your mousetrap car and record it in the space below.

Measuring Kinetic Energy – Day 11

Kinetic Energy (KE) is the energy of motion, which may be horizontal, vertical, or spinning

motion. To calculate the KE of a moving object, use the following formula:

Example:

Questions:

1. A Wooden mousetrap car weighs 500g and is moving at a speed of 2m/s. Calculate the kinetic energy (in Joules) of the car.

2. A ping pong ball has a mass of about 2.45 grams. Suppose that Forrest Gump hits the ball across the table with a speed of about 4.00m/s. What is the ball’s KE?

3. Determine the kinetic energy of a 625Kg rollercoaster moving with a constant speed of 18.3 m/s.

4. Determine the kinetic energy of YOUR mousetrap car.

a. Mass of your car – _____________ b. Speed of your car m/s (Use your average speed from Day 10) _____________ c. Calculations:

d. Final Answer:

Measuring Work – Day 12

The work done on the mousetrap arm is found using the formula W = F d, where F is the force (in Newtons) applied to the mousetrap car spring arm and d is the distance (in m) through which the force is applied.

In order to find the force (Newtons) applied to your lever arm, you need to use a spring scale and calculate how much force it take to pull your lever arm to the “ready” position. You may find the force is NOT the same through the entire range of motion, so check the force in several places. Be sure to use simple degrees as your increments (23.5°, 45°, 68.5°, 90° etc)

Angle (°) Force (N)

Average Force Applied:

To find the distance you pulled back you have to use the length of the mousetrap arm.

Write the length of the mousetrap arm here: ___________.

We need to find out what part of the circumference of a circle the force was applied to the mousetrap arm. The maximum would be half a circle (180°) if the mousetrap started at one end and completely unwound to the other end.

If it didn’t (and probably it didn’t go through the entire 180°), we need to find out how much it did go through.

STEP 1: Find out the circumference of the circle the mousetrap arm would make if it made an

entire rotation. C = 2r = ________________ m

STEP 2: Divide your circumference by 2: C 2 = ________________ m STEP 3: Now if it didn’t go through the entire half circle, estimate how much of the half-

circle the arm goes through before it stops. Choose one of the following percentages:

10% 20% 30% 40% 50% 60% 70% 80% 90%

STEP 4: Now multiply your half-circumference value by the decimal equivalent of the percentage. EX: If your mousetrap car arm went through 20% of the half circle (see picture at right), then your

final distance, d, will be C2 0.20

Write your distance here: d = ____________ m STEP 5: Now find the work done by you to move the mousetrap arm into position.

W = F d = _______________ Joules (the unit of work and energy)

Measuring Speed and Velocity - Day 13/14

Today, we will be determining the speed of your car! Think about driving in your car. How do we calculate speed? Speed is calculated in Km/h of course. To determine the speed or velocity of your car, we need to understand a view terms. Speed – the distance travelled by your car during a given time interval divided by the time interval. Velocity – the displacement of your car during a time interval divided by the time interval. NOTE: Direction will be the same in both cases.

TASK: Read Pages 182 and 183 in your textbook to help you understand the difference between speed and velocity. Procedure:

1. Take a piece of string 5m long and tape it to the floor at each end. 2. Use a meter stick to mark out 1m increments along the string. 3. Open the “timer” on your phone.

4. Have one person stand directly over the first meter mark, so they can see when the wheels pass that point. The timer should move with the car as it goes along.

5. Have one person start the car at the beginning point with the front wheels touching the start line. 6. Run your car. When the front wheels touch the 1m mark, hit “Lap” button. 7. Move along with your car, so your eyes are above the front wheels and you can see the front wheels pass

over the tape. When the wheels reach the 2m mark hit the “Lap” button. (These will be your interval times t1, t2, t3, etc.)

Test your car a minimum of 3 times in the hall. Record the distance traveled at each time interval for each trial.

Interval Times

Trial # t1 t2 t3 t4 Total (s)

1

2

3 4

5

AVG:

Speed (Use your total time from the previous graph to complete this chart)

Trial # Time (Seconds) Distance (meters) Speed (s = d/t)

1

2 3

4

5

AVG:

Velocity (See your above time trials for more information)

Trial # Time (Seconds) Distance (meters) Velocity (v = d/t)

1

2 3

4

5 AVG:

1. What is average speed of your car over the 5 meter displacement?

2. What category did you build your car to compete in? _________________ a. How does the speed of your car fit with your choice of category? For example, if your car

travels a speed of 0.46m/s, is that a better fit for the speed or distance category?

3. Speak to three other groups and write down the speed of their car was over the same displacement. a. ____________________ b. ____________________ c. ____________________

4. How does the speed/velocity of your car compare with the other groups?

5. What changes do you need to make to your car to be more competitive?

Graph the results in the table below. Make sure to label each trial in a different color. Include a legend!

X-Axis (horizontal): Time – (seconds) Y-Axis (vertical): Position (meters)

________________________________________________

Analysis:

1. Was the speed/velocity constant for each of the trials? How do you know? (Hint: Slope) __________________________________________________________________________________________________________________________________________________________________________________________

2. How can you determine if it was? (Hint: Slope) __________________________________________________________________________________________________________________________________________________________________________________________

3. If the velocity was constant, what would it look like on a graph? Use graph A, B and C to show positive uniform velocity, negative uniform velocity and non-uniform velocity respectively.

4. How far was your vehicle being pulled by the string? From the graph, is it possible to determine when the string was no longer pulling your vehicle? Explain.

A B C

__________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ 5. What was your vehicles maximum speed over the timing distance? When did this occur? __________________________________________________________________________________________ __________________________________________________________________________________________ 6. Discuss your findings with two other groups. What was the speed/velocity of their car? Based on these

discussions, are there any changes you are going to make to your mousetrap car? Note the changes below. ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Measuring Acceleration – Day 15

Acceleration – any change to the velocity of an object during the time interval. The change can be positive (increase) or negative (decrease). Since velocity is a vector quantity, then acceleration is a vector quantity.

NOTE: S2 means that the velocity is changing by x meters/second every second EXAMPLE: 1. A drag car reached a speed of 145.08 m/s in 4.48s. What was the dragsters average

acceleration? Assume it is in the positive direction.

For this day, we do not need any new calculations. All we have to do is take the velocity (which you found in on Day 10 – Speed and Velocity) and input it into the formula above. Procedure:

1. Using trial number one from speed and velocity, input the velocity of your car. into the this calculation to find acceleration for trial 1 below.

2. Using trial number one from speed and velocity, input the velocity of your car. into the this calculation to find acceleration for trial 2 below.

Trial Number Time (Seconds) Δt Δv Acceleration

1

2 3

4 5

AVG:

Mousetrap Car Physics Analysis Report – Day 16/17/18

Answer the following questions completely (include formulas and/or calculations where appropriate). Your answers may be written or typed and a minimum of 300 words.

Types of Energy: (Background)

1. Energy exists in a variety of forms – List nine examples of the various forms of potential and kinetic energy. Place a (P) if it is potential energy and (K) for kinetic.

2. Describe how potential energy was transformed to kinetic energy in your mousetrap car.

3. Explain that in the absence of resistive forces, motion at a constant speed requires no energy.

Thermodynamics:

4. Using Newton’s Three (3) Laws of Thermodynamics, explain the energy conversions that were occurring in your car.

5. Using the 1st and 2nd Laws of Thermodynamics, explain why combustion engines are not 100% efficient? (Hint: Think of thermal energy)

6. What are the two types of friction that affect the performance of your vehicle? 7. What problems related to friction did you encounter and how did you solve them?

Design/Materials: (Procedure)

8. What factors did you take into account to decide the number of wheels you chose in

your design? 9. What kind of wheels did you use on each axle? What is the effect of using large or

small wheels? 10. Discuss the effect of the length of the lever arm in the pulling force of your vehicle. 11. How is the balance of a wheel, around its center, related to the vehicle’s

performance? 12. How does the distribution of weight of the vehicle affect the traction of the wheels? 13. How does the placement of the mousetrap affect the performance of your vehicle? 14. Discuss the major problems encountered in the performance of your vehicle and

what did you do to solve them. 15. Explain how the process of design and redesign led you to the current model of your

car? How does this idea apply to science?

Calculations:

16. How is displacement used in the calculation of velocity? How is this different from the calculation of speed?

17. How did the speed of your car compare to other groups? 18. How did you find the acceleration of your car? 19. Looking back over your calculations, list the scalar and vector quantities.

a. Explain the main difference between scalar and vector quantities

Conclusion:

20. Comment on the efficiency of your mousetrap car. (Useful vs wasted energy) 21. If energy cannot be lost in the conversion, where did your energy go? Why is your

output not equal to the input? 22. List the modification you have made throughout your build and why you made them.

What were you trying to overcome with the change?

Extension (Optional):

Can you produce graphs of the cars position, velocity and acceleration against time. (Three graphs) Can you explain the shape of these graphs?