SOL: PS. 10
I. Work
A. Definition- transfer of energy that
happens when a force makes an
object move
B. Two conditions needed to have work:
1. a force must be applied
W
2. object must move in the same
Fxd
direction as the applied force
C. Formulaà work = force x distance
D. Unitsà joules (J) or newton*meter
E. Example for calculating work:
*Jamie raises a 500 N barbell a
distance of 2 meters. How much
work was done?
W = 1000J
II. Power
A. Definition- rate at which work is
done
W
B. Formulaà power = work/time
Pxt
C. Unitsà joules/second or watts (W)
D. Example for calculating power:
* A mover does 240J of work in 60s.
How much power was used?
P=4 W
III. Mechanical Efficiency
A. Definition- compares work output
to work input
B. Formulaà (output/input) x 100
C. Unitsà %
D. Can a machine be 100% efficient?
1. No, friction reduces efficiency
2. Oils/grease reduce friction
E. Example for efficiency:
*A person puts 80J of energy into
using a pulley to get 70J of work
done. What is the mechanical
efficiency?
ME = 88%
IV. Machines
A. Simple machine- machines that does
work in one motion
B. Types of simple machines
1. Inclined plane
2. wedge
3. screw
4. lever
5. pulley
6. wheel & axle
C. Compound machine- two or more
simple machines working together
Ex. Bicycle
D. Mechanical advantage – number of
times a machine multiplies your force
1. Machines increase the applied force
and/or change the direction of the
force
2. Effort force - force applied to the
machine
3. Resistance force - force applied by
the machine