List the six classic simple machines
inclined plane
wedge
wheel and axle
lever
pulley
screw
(Of these, the inclined plane, lever, and pulley are most frequently tested on the MCAT.)
Mechanical advantage is the ratio of magnitudes of the force _____ to the force _____.
exerted on an object by a simple machine (Fout)
actually applied on the simple machine (Fin)
Mechanical advantage equation
Units = dimensionless (ratio of two forces)
Applying a lesser force over a greater distance to achieve the same change in position (displacement) accomplishes the _____.
same amount of work
Free body diagram of a simple two-pulley system
All simple machines can be approximated as conservative systems if we ...
...ignore the (usually) small amount of energy that is lost due to external forces, such as friction.
The ideal pulley is _____ and _____.
massless and frictionless
Real pulleys—and all real machines, for that matter—do not ...
... achieve 100 percent efficiency in conserving energy output to input.
Efficiency of a machine equation
The percentage of the work put into the system that becomes unusable is due to _____ or _____ forces.
nonconservative or external forces.
System of six pulleys
1. What would be the force required to raise the weight?
2. What would be the displacement of the rope?
1) 1/6 * mg
2) 6*L