# Torque

## Overview

• Rotational or twisting force (τ,"tau")
• The product of force, distance, and the angle between force and lever arm
• τ = F · d · sinθ
• In the applications we will discuss today, the force and lever arm will be perpendicular
• ∴ θ = 90 and sin90 = 1
• so we get
• τ = F · d
• Given a fixed forque,
• Larger distance → less force
• Smaller distance → more force ## In Levers

• Key principle in levers (fulcrum, load, force)
• First class: Crowbar
• fulcrum between load and force
• Second class: Wheelbarrow
• load between fulcrum and force
• Third class: Tweezers
• force between fulcrum and load  • You can add and subtract torques when multiple forces are acting about the same pivot point (eq. raising or lowering a wheelbarrow)
• When the system is static (wheelbarrow is not being raised or lowered, such as while you are moving it from point A to B), torques are equal
• The amount of load you can lift is dependant on the ratio of d1d2
• τ1 = τ2
• F1 · d1 = F2 · d2
• F2 = d1d2 · F1 