Introduction to Machines Machines Force Work Mechanical Advantage

Machines Machine device that makes work easier changes the size and/or direction of the exerted force

Force Input Force (Fin) force applied to the machine “what you do” aka- effort force Output Force (Fout) force applied by the machine “what the machine does” aka resistance force

Work Win = Fin × din Wout = Fout × dout Work Input (Win) work done on a machine Win = Fin × din Work Output (Wout) work done by a machine Wout = Fout × dout

Work Fin × din = Fout × dout Win = Wout Conservation of Energy can never get more work out than you put in trade-off between force and distance Win = Wout Fin × din = Fout × dout

Work Win = Wout Win > Wout In an ideal machine... But in the real world… some energy is lost as friction Win > Wout

Mechanical Advantage Mechanical Advantage (MA) number of times a machine increases the effort force MA > 1 : force is increased MA < 1 : distance is increased MA = 1 : only direction is changed

Mechanical Advantage Fin F0ut MA Fin = 20 N MA = Fout ÷ Fin A worker applies an input force of 20 N to open a window with a resistance force of 500 N. What is the crowbar’s MA? GIVEN: Fin = 20 N Fout = 500 N MA = ? WORK: MA = Fout ÷ Fin MA = (500 N) ÷ (20 N) MA = 25 MA F0ut Fin

Mechanical Advantage Fin Fout MA Fin = ? Fin = Fout ÷ MA Fout = 2000 N Find the effort force needed to lift a 2000 N rock using a jack with a mechanical advantage of 10. GIVEN: Fin = ? Fout = 2000 N MA = 10 WORK: Fin = Fout ÷ MA Fin = (2000 N) ÷ (10) Fin = 200 N MA Fout Fin