1. Introduction to Machines Machines Force Work Mechanical Advantage

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

3. 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

4. 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

5. 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

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

7. 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

8. 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

9. Mechanical Advantage Fin Fout MA Fin = ? Fin = Fout ÷ MA Fout = 2000 N
Find the effort force needed to lift a 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