Pre-AP Physics Project: Falling Mass Powered Car
Purpose: To design and build a vehicle powered by a falling mass that will successfully carry a driver over a specified distance.
Partners: Students may work individually or in groups of 2 (must be in the same class).
Rules:
1. Maximum Dimensions: 24” long x 24” wide x 36” tall
2. Maximum Falling Mass: 1000 g = 1 kg (student brought masses will be checked before competition)
3. Materials: any available material may be used
4. Minimum Number of Wheels: 4 (all must be functional)
5. Driver must be able to “see” the road.
6. Driver’s compartment must be accessible (driver must be able to get in and out).
7. Driver must travel the entire distance without harm.
8. Vehicle must start from rest.
9. Vehicle must have a starting mechanism.
10. Vehicle must get its power from only the falling mass.
Background Information:
The drive mechanism is driven solely by a falling mass. The total potential energy just before the launch can be calculated using PE = mgh, where m is the mass in kg, g is the acceleration due to gravity, and h is the initial height of the falling mass. Since all things in the Universe obey the Law of Conservation of Energy, the potential energy going in is equal to the kinetic energy coming out (PE = KE). To sum all of this physics jargon up, the maximum energy your vehicle can use is limited. The key to success is to make your vehicle as efficient as possible and your two biggest enemies are weight and friction.
Anatomy of a Falling Mass Car:
A basic falling mass powered vehicle consists of the following basic parts: a chassis, a drive mechanism, wheels and the driver’s compartment. If proper care is not used to ensure that each system is functioning at its peak, your vehicle may not perform adequately, or at all.
The Chassis: The chassis is the part of your vehicle to which all other parts are mounted. It consists of a form defining frame and any necessary support structures for your other systems.
Keys to success:
1. Make it true – vehicles that run straight have the best chance
2. Make it light – lighter vehicles will travel farther with less force
3. Make it adjustable – things do not always go as planned
The Drive Mechanism: Without a drive mechanism your vehicle is nothing more than an over-engineered paper weight. The drive system is the heart of a successful vehicle. Great care and thought should be taken to design and build it right.
Keys to success:
1. Take advantage of physics
2. High highs and low lows – the secret to a strong drive mechanism is squeezing the most energy from the falling mass. You want to get the mass as close to the ground as possible.
3. Choose your design carefully; some possible designs are pictured on the next page.
The Starting Mechanism: Your vehicle must have some type of starting mechanism. You can utilize a trap door, a pulled pin, a removable chock, etc. You may not drop the mass by hand.
The Wheels: Do not write off the wheels as superfluous detail, they are just as important as the rest of your vehicle, and remember all wheels have to be functional.
Keys to success:
1. Light and Straight: keep your wheels as light and strong as possible. Make sure they are mounted perpendicular to the axel and true to the center so they do not wobble as they roll which uses up energy.
2. Friction: Your wheels need to have friction with the floor(so they can grip it), but your axels need to have as little friction as possible.
3. Size Matters: The diameter of your wheel is a major factor in overall performance. Torque is a turning force calculated by T = F x d. F is the force and d is the distance from the center of rotation. At any given time your drive system is going to place a constant torque on your drive axel. We can assume this torque to be constant. Since F and d are inversely proportional, as you increase the radius of your wheel, you decrease the forward propulsion force produced by its turning. However, increasing the wheel radius also increases your wheel’s circumference, thus reducing the number of turns required to get your car to the end of the track. (Simplified à Small wheels provide greater torque/force but require more turns
Quicker starts, quickly expended PE
à Larger wheels provide less torque/force but require fewer turns
Slower acceleration that can occur over a long distance
The Driver’s Compartment: Must be designed so that the driver can not only ‘see’ the road, but can get in and out as well. It should be designed with the driver’s welfare at stake since they must be able to survive the journey. The drivers will be fresh, non-boiled, large eggs.
Grades:
1. Design (Major Grade)
· Students are to build their own vehicles.
· Students will submit design drawings showing a side view and overhead view.
· Vehicles should be identical in design to submitted diagrams(add in modifications if needed)
· Designs must conform to specifications as outlined in the rules section.
· Designs will be judged by a panel of teachers
· Highest Possible Score = 100 points
2. Photogenic Competition (Major Grade)
· Vehicle will be judged according to visual appeal and appearance.
· Vehicles must meet previous specifications to be considered for competition.
· Vehicles will be judged by a panel of teachers and ranked on a scale from 1(best) to 10(worst)
· Total points will be compiled with the lowest score being ranked 1st.
3. Cost Analysis (Major Grade)
· Students are to prepare and present a cost analysis for their vehicles.
· It should include all materials used and where items were purchased or obtained.
· Must include individual item pricing, not just a total.
· Complete cost analysis and total must be turned in before competing or you will be disqualified from competing
4. Distance Competition (Major Grade)
· Student vehicles must travel a straight line distance of 30 feet on the due date to receive full credit.
· The distance for full credit will increase by 2 feet per day after the due date.
· Vehicles traveling shorter distances will result in a loss of points.
· Vehicles must travel a minimum of 20 feet or they will not receive credit for this project.
5. Survivability (Major Grade)
· All or nothing; your driver must survive the trip.
6. Overall Project Performance (Major Grade)
· This grade is determined from the average of the previous major grades.
· Reflects the overall performance on this project
7. Participation (Daily Grade)
· Students receive credit by completing the assignment
8. Sportsmanship (Daily Grade)
· Students exhibit sportsmanship during the competition phases.
· Students should be supportive and offer assistance whenever possible.
9. Deadlines (Daily Grade)
· Students receive full credit for meeting all assigned deadlines.
Scoring:
· This project consists of 6 Major Grades and 3 Daily Grades. Failure to complete this project will result in potential failure for the current six weeks grading period.
· Your vehicle must go a minimum distance of 20 feet to receive any credit for this project.
Major Grades:
Design 0-100
Photogenic
1st 100
2nd 97
3rd 94
4th 91
Cost Analysis 0-100
Distance Competition (Distances will increase by 2 feet for each grade for each day late competing)
30 ft 100
28 ft 90
26 ft 80
24 ft 70
22 ft 60
20 ft 50
< 20 ft 0
Survivability 0 or 100
Overall Project Performance 0-100
Daily Grades:
Participation 0-100
Sportsmanship 0-100
Deadlines 0-100
Helpful Hints:
· Start Early
· Test your vehicle regularly
· Don’t get paint/decorations in or on your moving parts.
· Make your vehicle easily adjustable.
· Devise a consistent release system
· Bring your vehicle up to school early if you are having problems (Help is more easily given when your vehicle is viewed)
· Good Luck
Due Dates:
1. Group Members Monday December 5th
2. Design Drawings Tuesday January 3rd
3. Cost Analysis Tuesday January 3rd
4. Distance Testing Tuesday January 3rd
5. Late Distance Testing Wednesday January 4th