2 Objectives: 1. To design and construct a mouse-trap car. 2. To design and use the mouse-trap as the motor or power source.3. To design and construct a car that will travel 20 feet.
3 Guidelines 1. Use regular mouse-trap. No rat-traps! 2. Mouse-trap MUST be mounted on car.3. Mouse-trap car MUST travel 20 feet.4. MUST use at least 10 parts, but no more than 20 parts.5. Mouse-trap car MUST start on its own power. NO PUSHING to get it started.6. Mouse-trap car MUST have at least 3 wheels.7. Mouse-trap car MUST use string from power source. No rubber bands!
4 Concepts to think about : 1. Friction & Resistance : How to over come them ?2. Traction & Leverage : These concepts are HUGE in solving the problem of distance and starting power.3. Weight vs. Strength.4. Craftsmanship : This concept is the difference between success and failure.
5 WARNING !Your mouse-trap car must travel 20 feet!
6 Design considerations Fast start vs. slow and steady ?What is the most effective wheel ?Light or heavy ?Big or small ?Thick or thin ?Platinum or gold ?Friction ? Where is it good and where is it bad ?How does the mouse-trap works as a motor or power source?Do you want a heavy or light car ?Does it matter where you mount the mouse-trap on the car?Does the car have to look pretty or cool ?
7 Power systems in mouse-trap cars 1. Potential Energy : The spring (at rest) is the potential energy.What is potential energy ?Stored energy or the ability to do work.2. Kinetic Energy : The moving spring is the kinetic energy.What is Kinetic Energy ?Energy of movement.
8 Hints1. Friction :The resistance to motion between 2 objects in contact with each other.Friction is good for wheel traction on floor.Friction is bad for all moving parts that must work together.Good craftsmanship is the solution to the problem!
9 Hints 2. Lever arm of mouse-trap: By adjusting the length of the mouse-trap’s lever arm, you can vary the force that is applied to the wheels of your car.Long lever arms DECREASE THE PULLING FORCE, WHILE SHORT ARMS INCREASE THE PULLING FORCE.
10 Hints Torque is a turning force. 3. TORQUE : When you turn a water faucet, open a door, or tighten a wrench, you exert a turning force.Torque is very important in getting your car to start under its own power. No pushing to start car.
11 Hints 4. Rotational Inertia : The property of an object to resist changes in its rotational state of motion.The greater the distance between the bulk of an object’s mass and its axis of rotation, the greater rotational inertia.It follows that the greater the rotational inertia of an object, the harder it is to change the rotational state of that object. If rotating, it is difficult to stop; if at rest, it is difficult to rotate.
13 Rotational InertiaIf you use a solid wheel – Easier to change rotation.Why ? Less rotational inertia because mass is more evenly spread out from center of wheel.If you use a spoke wheel – Hard to change rotation.Why ? More rotational inertia because mass is concentrated on the outside, far from center.
15 Summary Have fun and use The Design Process to solve the problems. It is not suppose to work the first few times….don’t give up!There are over 55 different concepts you need to over come.You got to remember that craftsmanship is really important.Use any materials you want.
16 You have 3 days to brainstorm and get some sketches down on paper. You have 15 days to construct your mouse-trap car.I am not impressed that you built a mouse-trap car…..Impress me by testing your car.20 feet ! No pity from me……….Good Luck !
17 Use The Design Process concept in your everyday life to solve any problem that you may encounter !