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NM Unit 6
Topic: Work and Energy
Learning Goals:
•Identify the types of energy that make up the total energy of a system
•Predict changes in mechanical energy when positive or negative work is done on the center of
mass
•Analyze a system and categorize the internal energy as potential, kinetic, or some combination of
potential and kinetic.
•Solve problems involving work, power, and/or energy
•Solve problems involving the Work-Energy Theorem
Work and Energy
Both scalar quantities
Both have units of Joules
Oh, and there is this weird equation thing...
Work changes energy?
What kind of energy (or energies) do we
have?
Specifically how can work change that type of
energy?
Work and Kinetic Energy
A 9kg bag is being pushed from rest 5m across
a smooth floor with a force of 11N. After being
pushed 5m the bag has a velocity of 3.5 m/s (a)
Calculate the work done on the bag (b)
Calculate the change in kinetic energy
Work and Potential
Energy
A factory worker lowers a 15kg crate from a
shelf 1.78 m above the ground to the ground.
The crate is being lowered at a constant
velocity. (a) What is the work done on the
crate by the worker? (b) What is the change in
gravitational potential energy of the crate?
Power and Energy/Work
Revisit
Power is the rate at which work is done or
energy is converted.
Watts are J/s
The wattage of something is the “conversion
rate”. A 60W lightbulb converts 60J/s of
electrical energy into heat and light.