Work
When a force acts on an object in the same direction the object moves.
Work Formula
Distance x Force
Work Units
Distance (meters) Force (Netwons) Work (Joules)
Power
The rate of doing work.
Increase power
Increase amt. of work done in given time or do given amt. of work in less time.
Power Formula
Work / Time.
Power Units
Watts
Horsepower
1 HP= 746 Watts
Machine
a device that changes a force, makes doing work easier
Changing Size of Force
Ex: Car Jack. A small force exerted over a large distance becomes a large force exerted over a short distance.
Changing direction of Force
Ex: Row Boat.
Changing distance of Force
Ex: Canoe. A machine decreses the distance through which you exert a force increasing the amount of work required.
Work input vs. work output
work output can never exceed work input because of friction.
Input Force
The Force you exert on a machine
Input Distance
The distance the input force acts through.
Work Input
Input Force x Input distance
Output Force
The work that is exerted by the machine
Work output
Ouput Force x Output distance
Work in = Work out when...
Ignoring friction
Mechanical Advantage
the number of times a machine increases an input force.
Actual Mechanical Advantage
The mechanical advantage that a machine provides by measuring the ACTUAL forces on a machine. Output Force / Input Force
Ideal Mechanical Advantage
the mechanical advantage that a machine would have without friction. Always more than AMA. Input Distance / Output distance.
Efficiency
the percentage of the input work that is converted to output work. Work Output / Work Input x 100. Reducing Friction increases efficiency.