1 why we use machines
- 1. Why we use machines
- 2. 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.
- 3. Ex: You apply effort force to a crowbar handle. The crowbar handle has resistance force on lid to open the crate.
- 4. 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
- 5. 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)
- 6. Work output can never be greater than Work input. It will always be a smaller number than Work input.
- 7. Ideal machine- machine in which work input equals work output. W in = W out (Fe X de) = (Fr X dr)
- 8. Mechanical Advantage (MA)- the number of times a machine multiplies the effort force. The higher the MA, the easier it is on you.
- 9. To calculate the mechanical advantage of any machine. Variable Ending Units Effort force (Fe) Newton Resistance force (Fr) Newton Mechanical Advantage None (MA)
- 10. Fr Fe MA . . . . x MA = Fr / Fe Fr = MA x Fe Fe = Fr / MA
- 11. 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
- 12. To find the mechanical advantage of a wheel and axle MA = radius of wheel / radius of axle MA = 5 / 1 MA = 5
- 13. To find the mechanical advantage of an inclined plane MA = Length of slope / Height of slope
- 14. To find the mechanical advantage of a pulley MA = Number of pulleys you see MA=1 MA=5 M A= 4 M A= 2