Why we use machines

Machine- device that makes work easier. 2 forces are involved when machine is used Effort force (Fe) The force applied to the machine. Resistance force (Fr) The force applied by the machine.

Ex: You apply effort force to a crowbar handle Ex: You apply effort force to a crowbar handle. The crowbar handle has resistance force on lid to crate.

There’s 2 kinds of work when a machine is used Work input (Win) Work done on the machine Work output (Wout) Work done by the machine

To calculate Work input Win= Fe X de (Win = effort force X distance) To calculate Work output Wout = Fr X dr (Wout = resistance force x distance)

Work output can never be greater than Work input Work output can never be greater than Work input. It will always be a smaller number than Work input.

Ideal machine- machine in which work input equals work output. W in = W out (Fe X de) = (Fr X dr)

Mechanical Advantage (MA)- the number of times a machine multiplies the effort force. The higher the MA, the easier it is on you.

To calculate the mechanical advantage of any machine. Variable Ending Units Effort force (Fe) Newton Resistance force (Fr) Newton Mechanical Advantage None (MA)

MA = Fr / Fe Fr = MA x Fe Fe = Fr / MA Fr . . MA Fe x

To find the mechanical advantage of a lever. MA = Length of effort arm / length of resistance arm MA = Le / Lr MA= 30m/10m MA= 3

To find the mechanical advantage of a wheel and axle MA = radius of wheel / radius of axle MA = 5 / 1 MA = 5

To find the mechanical advantage of an inclined plane MA = Length of slope / Height of slope

To find the mechanical advantage of a pulley MA = Number of pulleys you see MA=1 MA=5 MA=4 MA=2