Notes 13-4 Machines and the body

Force A push or pull on an object Described by magnitude (strength) and direction Unit = Newton

Work You do work when you exert a force on an object that causes it to move in the same direction as the force Work = Force x Distance Example: Lifting a box 2 meter using a force of 20 Newtons. Work = 20 N x 2 m = 40 N  m

Machines Machines allow you to do work easier and more effectively A lever is a simple machine that makes lifting heavy objects easier.

Levers A lever is a ridged bar that is free to pivot, or rotate, on a fixed point (fulcrum)

Anatomy of the lever Fulcrum – point around which the lever rotates Input Force (Effort Force)– Force exerted ON the lever Output Force (Resistance Force) – Force exerted BY the lever

Levers Levers are classified according to the location of the fulcrum relative to the input (effort) and output (resistance) forces.

Mechanical Advantage Number of times a lever increases a force exerted on it Mechanical Advantage = Resistance Force Effort Force Example: Calculate the mechanical advantage of the lever that’s uses 60 N to move a 120 N box. MA = 120 N ÷ 60 N = 2 (the lever doubled the effort force)

Levers and the human body Your body contains muscles attached to bones in ways that act as levers. Here the biceps muscle attached in front of the elbow opposes the muscles in the forearm. Can you think of other muscle levers in your body?

Simple Machines in the Body Most of the machines in your body are levers that consist of bones and muscles. Joints act as fulcrums, bones acts as levers, muscles provide the force

Animation on levers body-moves/revise-it/levers body-moves/revise-it/levers Video on Levers: D= D=129086