http://www.ck12.org Chapter 8. Work, Power, and Simple Machines
C = 2 supporting strands; IMA = 2
D = 3 supporting strands; IMA = 3
E = 3 supporting strands; IMA = 3
If the direction of the effort force is in the same direction and the movement of the load, the effort strand will be a
supporting strand. If the direction of the effort force is in the same direction as the resistance force, the effort strand
is not a supporting strand. Look again at the five pulley systems to ensure this is true.
Example Problem: Consider the pulley system sketched above. Given that the resistance force is 8500. N, find
(a) the IMA.
(b) the ideal effort force required to list this weight.
(c) the distance the weight will rise if the effort force moves 1.0 m.
(d) the AMA if the actual effort force is 2000. N.
Solution:
(a) Since the effort strand moves in the opposite direction of the resistance, it is not a supporting strand. Therefore,
there are 5 supporting strands and that makes the IMA = 5.
(b) Effort force=resistance forceIMA =^85005 N=1700 N
(c) Since the IMA is 5, the resistance distace will be 1/5 of the effort distance: the resistance distance is 1.0m/5 =
0.20 m
(d) AMA=resistance forceeffort force =^85002000 NN= 4. 25
Wheel and Axle
Just like it sounds, a wheel and axleis composed of two connected cylinders of different diameters. Since the
wheel has a larger radius (distance) than the axle, the axle will always have a larger force than the wheel. The ideal
mechanical advantage of a wheel and axle is dependent on the ratio between the radii:
IMA=Radius
wheelRadius
axle