Why we use machines Machine device that makes

Why we use machines

§ Machine- device that makes work easier. 2 forces are involved when machine is used 1. Effort force (Fe) The force applied to the machine. 2. Resistance force (Fr) The force applied by the machine.

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 1. Work input (Win) Work done on the machine 2. 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. 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 x Fe

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