Machines

Event Information

In this physics event, participants answer questions relating to genetics and heredity. Click here for rules!

Useful Overview

• https://scioly.org/wiki/index.php/Machines

This event will be test only for this year.

Overview

Type of Event: Study Event

Competitors: 2 participants

Materials Required: 3-ring binder of any size, 2 calculators of any type

Competition Checklist: 3-ring binder of any size, 2 calculators of any type, pencils & pens

What To Study

It is useful to have a little bit of physics background, but the best way to study is to do past tests, since the binder can contain a lot of information

Useful equations:

• Force: F = ma (mass times acceleration)

• Work: Work is essentially the "total" amount of force applied. It is calculated by W = F * delta S = |F||delta S| cos theta, where S is the distance travelled by an object and theta is the angle between the force and the distance travelled vector. The work done is the same as the amount of energy put into a system.

• Mechanical advantage: ratio of the output force to input force. Machines allow an input force to be magnified to get out a larger output force, but the total amount of work is the same (the input force * original distance = output force * new distance)

  • Mechanical advantage is MA = F_o/F_i, where F_o is the output force and F_i is the input force.

    • Ideal mechanical advantage is the mechanical advantage in an ideal world: a world without friction or wear on the machine. The formula is IMA = d_i/d_o. So this is the same as F_o/F_i, since F_o*d_o = F_i*d_i.

    • Actual mechanical advantage is experimentally determined as F_o/F_i.

• Efficiency captures how much energy is lost to friction, and is W_o/W_i, where W_o is the output work and W_i is the input work. Efficiency is always less than 100%, since energy is lost. It can also be measured equivalently as AMA/IMA.

• Torque is the equivalent of force for rotational movement: it is T = F * d = |F||r| cos theta.

• Power is work per time, or P = W/t.

Remember:

• Conservation of energy: energy is always conserved, but it might escape as heat or sound energy

• Types of machines:

  • Pulleys

  • Belt & Pulley

  • Inclined Planes

  • Wheel & Axles

  • Levers

  • Wedges

  • Screws

  • Compound Machines