Mission Possible B

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This page is about the Mission Possible competition for Division B. To find information about Mission Possible for Division C, or to learn more about different types of energy transfers for enrichment, please see Mission Possible C.

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


Mission Possible is all about using simple machines to create a chain reaction, using a number of tasks designated by the rules to achieve the maximum points.

This type of machine is called a Rube Goldberg device. A man named Rube Goldberg made up this type of machine, and so it was named after him. Basically, a Rube Goldberg machine implements a way to finish an often simple task in a very complicated fashion.

For example, a machine might start with the opening task, which was, most recently, using a plunger.. The hit front the plunger might knock down a domino, which might land in a pulley that pulls an object a few centimeters. The pulling of the object would hit a lever which would open a flap that would allow a ball to roll down a ramp, hitting a mousetrap that would then release a string with a weight on it, which would hit another lever and raise an object, and so on and so forth until you reach the final task, which was raising a flag in 2016. However, this example machine doesn't use all the simple machine transfers (there are a maximum of 18 storable transfers), so it is not ideal. This is a frustrating event at times, since it requires a lot of testing and tweaking.

The challenging part of this event is not building the machine, but making it reliable so it works every time. Since it is not ideal for anything to have to intervene after the reaction has started, the reaction should seamlessly work on its own every time.

Simple Machines

There are six types of simple machines. They are:

  • Lever
  • Inclined Plane
  • Wedge
  • Screw
  • Wheel and Axle
  • Pulley


Levers are one of the most commonly used simple machines in both everyone's daily lives and this event. There are three types of levers, called first class, second class, and third class. First class levers are probably the kind that most people think of when thinking of a lever–the fulcrum is in the center, and the load goes on one end and the force on the other. Some real-life examples of first class levers are pliers and a hammer (when using it to pry up a nail). In the pliers example, the hinge on the pliers becomes the fulcrum, the load is enclosed in the jaws of the pliers and the effort comes from the hand squeezing the handles. Next, is the second class lever. This lever has its fulcrum on one end, with the load in the middle and the effort on the other side. Two prominent examples of this lever are wheelbarrows and nutcrackers. To go more in-depth, imagine a wheelbarrow. There are handles to hold on to, or where one provides the effort. The wheels provide a point of balance–in other words, a fulcrum. And, of course, the load, the mulch or dirt that is being carried, is in between. Finally, the third class lever is similar to the second class except that it has the effort in the middle and the load on the end. A great example would be an arm- the elbow is the fulcrum, the load would be whatever is being held in the hand, and the effort comes from the forearm.

A free body diagram of an inclined plane

Inclined Planes

Another common simple machine is the inclined plane. This simple machine uses a ramp that lessens the force needed to get something the same distance off the ground as if you were just lifting it. In the Science Olympiad rules, inclined planes must have an object pushed or pulled up them (NOT down, as this would be too easy to accomplish. Inclined planes in real life include wheelchair ramps, staircases, and slides (though that goes downwards).


Although wedges may look somewhat similar to an inclined plane in theory, in practice they work quite differently. Wedges allow you to push two objects apart more easily (or to split an object in half). When the wedge is pressed in between two objects in your machine, it should separate the two, not just push slightly and cause something to fall because of gravity. There are many real-life applications of wedges, including knives, nails, and axes, to name a few.


Sometimes less commonly used in the event, screws are a simple machine that convert rotational force to linear motion. They accomplish this task through threads with a certain pitch (in more commonly used terms, ridges with a certain angle relative to the body of the screw) that force the screw farther into its hole. The main real-world examples of screws are, well, screws, along with threaded rods (this rotational to linear motion is what allows for many braking systems in vehicle events) and the moving part of vises.

Wheel and Axle

A wheel and axle is a simple machine that consists of a wheel attached to an axle (think about cars) and transfers energy from one part to another. This part is often very challenging to get right. First of all, you cannot just roll a wheel attached to an axle down an inclined plane. That would be an example of only one force, the wheel and axle combined, in one directional force. For a wheel and axle to be legal, the forces have to oppose. A common example for this is a windlass[1]. This involves an axle inserted into a vertical surface and a wheel put onto the axle so that it can spin, and attaching a string to the axle, so that if the wheel spins, the axle does also, pulling the string. Since the axle is staying put, opposing the force, or the wheel, and transferring energy via the string, then this would be a legal and functioning wheel and axle.


A pulley is a wheel and axle that changes the direction of a force with a mechanical advantage[2] to transfer energy. As with a similar wheel and axle, this is a very challenging simple machine to get right. First of all, the definition of a pulley is often confusing. It cannot just be a wheel and axle with a string on one side and a weight on the other. It has to have a mechanical advantage, or a benefit of saving energy, to be considered a pulley. The mechanical advantage of a pulley is the number of parts of the string that act on the force. An example of this fitting into a Mission Possible device is sliding a piece of wood out from under a weight attached to one side of a string, using three wheels and axles and a length of string to lift another, lighter, weight that lifts up to send a ball rolling down a ramp and up an inclined plane.



While it may be tempting to fill a machine with many levers and other more common simple machines, in order to maximize points, teams should try to include as many of the types of simple machines as they can. Point will be rewarded for each unique transfer (counting each class of levers separately).


A device will need to run as close as possible to the Target Time provided by the Event Supervisors at the competition. While some devices might naturally take a long time to run, most will only take a few seconds. It is important to implement a way to adjust the time each run takes, which may not (and probably won't) be a simple machine. Often, these parts of devices include a substance such as sand or rice going through a small opening, building up and eventually becoming heavy enough to trigger the next task. However, these methods can be inconsistent, and many other ways are possible.


Another important component of this event is writing a Transfer Sequence Log, or TSL for short. This document lists all transfers, including the start and end task, and how many points they're worth (even if they're repeats and worth nothing), as well as a brief description of each. It's worth points, so not doing will result in a lower score.

Yearly Task

Most recent years have included one or more tasks that the device must complete, either to start the device, during the run of the device, and/or when completing the device run. These predetermined tasks generally vary from year to year in order to ensure that teams need to address a new engineering challenge every year.

Starting Tasks

The current starting task:

  • Dropping a golf ball into the device so that it initiates the next action

Some start tasks in recent years have been:

  • Dropping a racquetball into the machine
  • Operating a plunger

The starting tasks often involve putting kinetic energy in your device in ways that might be very variable depending on how you do them each time. For instance, you could accidentally pull your plunger back a different distance every time if you were not careful about it. This could create errors in your device's run. You should try to figure out a way to make your start task the same every time.

Ending Tasks

The current ending task:

  • Moving a golf ball on to a golf tee

Recently, some of the ending tasks have been:

  • Raising a flag
  • Ringing a bell

Generally, the ending tasks involve something the judges can either hear or see- some kind of output. It is important to make sure that your task is obvious when it is completed-this is important not only for timing of your device but, in the case of the bell, actually getting the points for that task. If, for example, your bell could not be heard ringing, you wouldn't get its points.

Things to Keep in Mind While Building

  1. Make sure to label each task within the machine with little pieces of paper. That's a requirement!
  2. 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.
  3. Make sure to meet the general requirements. Teams that fail to do so will be placed in the second tier. Make sure that all parts of the device, including the outer walls and base plate fall within the legal dimensions of the device.
  4. Be safe by using a mechanical timer to achieve as close to the ideal time as possible. One method would be to use a long screw to eat up time. This way, the time it might take to finish that particular task can be adjusted.
  5. No loops or parallel paths are permitted in the device. Make sure that the action is linear from start to finish.
  6. The highest part of the device automatically designates the top boundary of the device.
  7. You can start and set parts of the device operating before the pulling of the string (such as pendulums, springs, etc.).
  8. Teams cannot touch the device after it has been started without losing points. This is why the reliability of the machine is important; there will be no need for interference.
  9. Don't forget your TSL! It is required, and gives easy points.
  10. Remember that you will probably lose any positive points for time if your device fails to complete the task, but continues to operate.
  11. Try to stay within the ideal time, but if that is not possible, better have it finish than fail!


  1. Know both the task sequence list and rules well enough to be able to explain everything.
  2. Go with the simplest way possible. Don't over-complicate things, creating more room for failure. Also, build things with a durability factor. There is more reliability this way.
  3. Draw all the designs and keep them together in case something doesn't work and need to build something new.
  4. Prepare for every scenario possible. Bring just-in-case items like tools or extra materials you need, but don't go overboard.
  5. Test the device prior to competition many times--do not just build it and bring it in.
  6. Always allow room for improvement. This will reduce the chance of failure if you keep it simple. Teams do not need to prepare a state-ready box for regional competition if it is not necessary.
  7. Practice with your partners and make sure that they know what they're doing!
  8. Teams can use small pieces from Erector sets or Lego sets to get gears (not legal for some tasks), pulleys, and plates of metal with holes pre-drilled.
  9. 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 are even cooler. However, they don't count for anything except maybe time (but there are easier ways to extend the run time of a device), and they affect the reliability factor of a machine. Stay with safer transfers and the tasks listed in the rules.
  10. Teams should ensure that everything needed is present. Make sure nothing is forgotten.
  11. Devise a system in which each of the people in the event has a designated part in setting up the machine so that the device can be ready as quickly as possible.
  12. And last but not least, know the rules. Teams should always have a copy of the rules during the competition to be able back themselves up for any doubts the event supervisors may have with the device.

See Also