1. February 8, 2011 Review from design process
U3b-L6
February 8, 2011
Review from design process
When testing an idea, what is the only way to know if your design will work in real-world conditions?
2. During the evaluation step of the design process, what do you do if your initial design doesn’t fully solve the problem or meet the challenge?
1. build a model or prototype and test it.
2. go back and repeat the problem solving steps, you’ll know
what doesn’t work and be in a better position to develop an
idea that does.

2. Mousetrap Car
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3. ENGINEERING DESIGN PROCESS
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ENGINEERING DESIGN PROCESS
Clearly Defined Steps:
Defining a problem
Brainstorming
Researching and generating ideas
Identifying criteria and specifying constraints
Exploring possibilities
Selecting an approach
Developing a design proposal
Making a model or prototype
Testing and evaluating the design, using specifications
Refining the design
Creating or making it
Communicating processes and results

4. Mousetrap Car A mousetrap makes use of a lever
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Mousetrap Car
A mousetrap makes use of a lever
Setting the mousetrap is a second-class lever
Releasing the mousetrap is a third-class lever
2nd Class
3rd Class

5. Mousetrap Car 1)Setting the Mousetrap.
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Mousetrap Car
                             
1)Setting the Mousetrap.
The load is the arm of the spring that is being pushed down to compress the spring.
The effort force is your fingers on the end of the snapper arm, and the fulcrum is the pivot point in the middle of the trap.
2)Releasing Mousetrap
Snapper arm becomes load
Sprint arm becomes effort force

6. U3b-L6
Mousetrap Car
When a mousetrap is set, the spring in the center is compressed, becoming a source full of potential energy.
This energy is being stored, not used, but as soon as the trap is released, it is converted to kinetic energy (the energy of motion) that propels the snapper arm forward.                                 

7. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
If you are trying to build a long distance traveling or fast vehicle you will need to think carefully about the following concepts: Energy, Power Output, Inertia, rotational inertia, friction, torque, and pulling force.

8. Mousetrap Car Physics Concepts
U3b-L6
Mousetrap Car Physics Concepts
If you are trying to build a long distance traveling or fast vehicle you will need to think carefully about the following concepts: Energy, Power Output, Inertia, rotational inertia, friction, torque, and pulling force.

9. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Energy
Energy is the ability to do work. Work is the applying a force to an object over a distance.
The goal of the project relies on efficiently transferring the spring’s energy to the car’s wheels. The concepts involved in the transfer of this energy rely on an understanding of simple machines.

10. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Energy Transfer
1)The trap acts as a lever to transfer the energy to the axle.
2)The axle acts on the wheel as a second transfer of the energy.
3)Finally, the energy is used to push the wheel against the floor, causing the car to move.

11. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Energy
Friction leads to a decrease in the efficiency of the machine and decreased performance.
Correct use of simple machines will increase your cars performance.

12. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Steps 3 & 4 – Brainstorm/ Research/ Generate Ideas
Power Output is how quickly the energy stored in the mousetrap is released.
Two approaches for long distance
Build a fast moving car that releases its energy quickly and then coast as far as possible.
Build a slow moving car that releases its energy slowly over the entire pulling distance.

13. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Steps 3 & 4 – Brainstorm/ Research/ Generate Ideas
Inertia is the resistance that an object has to a change in its state of motion.
A heavy car will require more pulling force than a lighter car for equal acceleration; lighter cars accelerate faster but heavy cars can coast longer

14. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Steps 3 & 4 – Brainstorm/ Research/ Generate Ideas
Rotational inertia is the resistance that a wheel or rotation object has to changing its state of rotation. Similar to inertia but dealing with a rotating object. The less rotational inertia that an object (wheel) has the less the torque that will be needed to change its state of rotation or the easier it will be to accelerate.

15. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Steps 3 & 4 – Brainstorm/ Research/ Generate Ideas
Friction is the resistance of motion between two objects.
Most friction between the materials in your car reduce the amount of energy that is used to move the car.
However, you actually rely on the friction between your wheels and the floor to help your car move.

16. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Steps 3 & 4 – Brainstorm/ Research/ Generate Ideas
Friction
Another, less thought of, friction involved in the performance of your car is air resistance.
Air resistance acts against the motion of the car and therefore should be reduced to increase performance.

17. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Steps 3 & 4 – Brainstorm/ Research/ Generate Ideas
Torque is a turning or twisting force.
To maximize your acceleration you want a shorter lever arm. Keep in mind that if your arm is too short the force will be large enough to cause the wheels to spin-out, wasting energy.
To minimize your acceleration you will want a longer lever arm.

18. Mousetrap Car Physics Concepts
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Mousetrap Car Physics Concepts
Steps 3 & 4 – Brainstorm/ Research/ Generate Ideas
Newton’s Laws
Newton’s first law is also known as the law of inertia.
Inertia is an object’s tendency to resist change.
Newton’s second law the equation F=ma.

19. Mousetrap Car Physics Concepts
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Steps 3 & 4 – Brainstorm/ Research/ Generate Ideas
Newton’s 1st and 2nd Laws
Should that the cars with larger masses need greater forces.
Also cars with larger masses take longer to slow down

20. Ideas for design
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21. U3b-L6
HOMEWORK
-Gather parts needed for construction. Construct the design in class tomorrow. -Study for TEST next week