Rube Goldberg Project

Rube Goldberg Paper

• Detail the energy transfers involved

• Discuss the simple machines used

• Include important design or production ideas

• Include any physics concepts you had to consider while completing the machine

• Not a description of the steps, rather a topical discussion of the physics involved.

Energy Transfers

• For the Rube Goldberg machine to work, energy must be transferred from the beginning to the end.

• Types of energy– Gravitational potential - Chemical– Elastic potential - Electrical– Kinetic - Thermal– Linear -

Rotational

Energy Transfers

• Potential to kinetic– Ball rolling down a ramp

Energy Transfers

• Elastic to kinetic– Slingshot propelling a marble

Energy Transfers

• Linear to rotational– Ball falling into basket connected to pulley

• A bar supported at a single point called the fulcrum.

• Position of the fulcrum changes the mechanical advantage.

• Manipulate the position of the fulcrum.

WHEEL & AXLE

• Any large disk (the wheel) attached to a small diameter shaft or rod (the axle)

• Can give you mechanical advantage.

• Example: Turning a screw with a screwdriver

• Any rope or cable looped around a support. – Example: A rope thrown over a branch to hoist

something into the air.

• Often incorporates a wheel and axle system to reduce the friction on the rope and the support.

• Gives mechanical advantage

• A ramp

• Allows you to exert less force at the price of a longer distance

• Same amount of work done, just seems easier because less force is needed.

• Two inclined planes placed back to back

• May be forced into an object to prevent it from moving or to split it into pieces.

• Example: A knife

• An inclined plane wrapped around a cone• Can be used to move a load (like a

corkscrew jack)• Used to fasten objects together because

of the great forces screws can exert

Complex Machines

• Derived from simple machines

• Combination and adaptation of simple machines

Mechanical Advantage

• Simple machines can provide MA.

• Ratio of output force to input force.

• MA = Output force = Input distance

Input force Output distance

Efficiency

• Real machines have friction

• Energy is dissipated as heat

• Never 100% efficient

• % Efficiency = Output work x 100%

Input work