Mission Possible B is an event in which teams make a Rube Goldberg device which uses certain tasks and runs as close as possible to the ideal time to gain the maximum number of points.

Physics of Simple Machines

Mission Possible is all about simple machines. What exactly is a simple machine? A simple machine is a machine that uses a concept to increase distance or power of a force. There are 6 types of simple machines.

File:Simplemachines.png

Wedge
Screw
Pulley
Wheel and Axle
Inclined Plane
Lever

Each machine is unique in its own way in that they can change the distance or power a force is applied in different ways. They also may change the direction in which a force is applied.

IMA

IMA stands for Ideal Mechanical Advantage.

Ideal Mechanical Advantage is the multiplier of the force from what was applied to the result force. So when you have an IMA of 2, that means that the force you applied was doubled by the simple machine. When you have an IMA of [math]\displaystyle{ 0.5 }[/math] or [math]\displaystyle{ \frac{1}{2} }[/math], that means that the force you applied was halved by the simple machine. When you have an IMA of 1, that means the force that you applied stayed the same. Key Concept: With simple machines, you exchange power with distance.

An example of an IMA of 2: If you applied 2 units of force for 4 meters, the result would be 4 units of force for 2 meters. This may seem confusing without a proper explanation and understanding of physics, but you can read a physics textbook if you want to fully understand the concept of simple machines. Now, let's take a look at each individual type of simple machine.

Pulleys

A pulley is an easy simple machine to implement. A simple pulley is a string around a mounted circular axle. A load can be attached to one end of the string. It would require the same amount of force to pull the load up as normal. You could balance it by putting an equal load on the other side. Take a look at this diagram:

This type of pulley is called a "gun tackle".

Imagine if you were to pull on the string with the little arrow. If you were to pull on it for 10 meters, the hook will rise 5 meters. This is because there are two strings that lift the hook and only one string that is being pulled. This pulley will have an IMA of 2. This means that you can lift a heavy load as if it were only half as heavy. Now, imagine if three strings were attached to the hook. The IMA would now be 3.

Pulleys are easily acquirable at your local hardware store. To make the circular part of the pulley, you could also use wheels from Lego sets (without the tires, of course).

Inclined Planes

"Inclined plane" is just a fancy word for a ramp. Finding the IMA of an inclined plane is easy. Simply divide the diagonal length of the ramp by the vertical length of the ramp.

The IMA of this ramp is 12 (60/5). Because the circle on the ramp is less than 12x heavier than the one hanging, the one hanging pulls the circle up the ramp.

Wheel and Axles

A wheel and axle is a simple machine that is used in the final task.

This diagram shows how to find the IMA of a wheel and axle simple machine. basically, you are dividing the radius of the wheel by the radius of the axle.

When you use a wheel and axle in the final task, there are two things to consider:

The longer the radius of the axle, the higher the mass (Fr in the diagram) will be raised.
Paddles will be attached to the wheel. Make sure the granular material falls onto the outer part of the paddle rather than simply fall into the crevice where the paddle is attached to the wheel, which would not cause any movement.

Levers

A lever consists of 4 elements- a flat board, the fulcrum (the stationary point on which the board pivots, usually resembles a triangle), the effort (the force or object that is usually pushing down) and the load (the force or object that moves as a result of the effort force). There are three types of levers.

First Class
- The fulcrum is in the middle, the effort is on one side, and the load is on the other. An example of a first class lever would be a seesaw.
Second Class
- The fulcrum is to one side, the load is on the other side, and the effort is in the middle. An example of a second class lever would be a wheelbarrow.
Third Class
- The fulcrum is to one side, the load is in the middle, and the effort is on the other side. An example of a third class lever would be tweezers.

To find the IMA of a lever, divide the distance between the fulcrum and the effort by the distance between the fulcrum and the load.

Wedges

Screws

Key Points

1. The action of each simple machine will determine which of the eight types of simple machines it is most like.

2. Find out when the Simple Machines List is to be given to the Tournament Director. Meet the deadline. Resist changing the device after this. Spend time perfecting the device.

3. Label the actual simple machines and make sure that the numbers match the Simple Machines List.

4. The simple machines of the same type do not have to be unique. Note that consecutive machines of the same type (even though unique) still only count as one machine.

5. Make sure to meet the general requirements, since failure to do so is a severe penalty (you get second tiered). Make sure that all parts of the device, including the outer walls and base plate fall within the legal dimensions of the device.

6. Be safe by using a mechanical timer. The sand and water in the pulley system should account for any needed use of extra time.

7. Do not use any loops or parallel paths in the device. Make sure that the action is linear from start to finish.

8. The highest part of the device automatically designates the top boundary of the device.

9. You can start parts of the device operating before the pulling of the string (such as pendulums, springs, etc.).

10. You will not be allowed to touch the device at or beyond the next-to-last simple machine. Make sure that this works every time.

11. Remember that you will probably lose any positive points for time if your device fails to complete the task, but continues to operate.

12. The only thing that should control how much the mass is lifted is the operation of the last paddle wheel ( no pulleys, motor, etc)

Tips

1) Know your task sequence list as well as you know your rules. Be able to explain everything.

2) Go with the simplest way possible. There is less to be fixed that way.

3) Draw all your designs and keep them together in case something doesn't work and you need to build something new.

4) Prepare for every scenario you can think of. Bring just-in-case items, but don't go overboard.

5) Test your device prior to competition many, MANY times--do not just build it and bring it in.

6) Practice with your partner and make sure that s/he knows what s/he's doing!

7) KISS! Keep it simple, stupid. This has been mentioned many times but it can not be stressed enough. Yes, domino trains are cool. Baking soda and vinegar inflating balloons is even cooler. However, they don't count for anything except maybe time (but there are easier ways to make your device go longer), so it would be a bad idea to use them. Stay with safer transfers and the tasks listed in the rules.

8) And last but not least, KNOW THE RULES. You can even tape them to your box if the event supervisor doesn't agree with something in your device to back yourself up.

Mission Possible B

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