Principles of Engineering
Unit 1.2.5 – Work, Energy & Power
Work
Work is the ____________ of the force (F) applied to an object over a distance (d) in which the object
travels as a result of the force.
Work = Force x Distance
W=FxD
The __________ (j) is the metric unit of work. One (1) Joule = one (1) newton·meter or N·m
Work Example
A student lifts a 50 pound(lb) ball 4 feet (ft) in 5 seconds(s). How many joules of work has the student
completed?
Convert English units to SI units:
1lb  4.45N
50.0lb  4.45  222.5N  223 N
1 ft  0.305m
4.00 ft  0.305  1.22m
Solve for Work
W = F x D or W = _______________ x ______________
Energy
Definition: The ability to do _________ (light, heat, mechanical, chemical, electrical).
Forms of Energy - Potential Energy
__________ or ______________ energy. The capacity to do work by virtue of position or configuration.
Forms of Energy - Kinetic Energy
The energy of ____________. The energy a body possesses because of its motion, which occurs
anywhere from an atomic level to that of a whole organism.
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Energy Transformation
The ______________ of one form of energy into another form.
Examples:
•
___________________ – Food is consumed and converted into motion for playing sports or
taking a test.
•
•
_____________ – Sunlight is consumed by plants and converted into energy for growth.
___________________ – Energy transferred to an oven is converted to thermal energy for heating
our food.
Renewable Energy Sources
_______________ _______________ ______________ ________________ _______________
Nonrenewable Energy Sources
_____________ _________________ ________________ _______________
Conservation of Energy:
Energy ___________ be created or destroyed, but it can __________ from one form to another.
Energy Conversion:
______________ one form of energy to another.
Energy ________________: The _______ of the useful energy delivered by a dynamic system to the
energy supplied to it.
____________: The _______ of energy during conversion.
Efficiency = ------------------------- x 100
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Energy Conversions:
Fossil fuels: Chemical → Heat → Mechanical → Electrical
Solar cells: Sunlight → Electrical
Wind turbines: Kinetic → Mechanical → Electrical
Hydroelectric: Gravitational potential → Mechanical → Electrical
Nuclear: Nuclear → Heat → Mechanical → Electrical
What Are Current Energy Concerns?
__________________ _________________ _________________ _________________ _________
What roles do engineers have in energy?
Power
Power is the ________ at which work is performed or energy is expended.
Power = -------------------
The ________ is the base unit of power.
One watt is equal to 1 joule of work per second.
Power is also measured in _________________ (HP).
Types of Power
________________ Power: Uses electrical energy to do work.
________________ Power: Uses mechanical energy to do work (linear, and rotary forms).
_________ Power: Uses energy transferred by liquids (hydraulic) and gases (pneumatic).
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Power Example
A student lifts a 50.0 pound (lb) ball 4.00 feet (ft) in 5.00seconds (s).
How many watts of power are used to lift the ball?
Power = Work / Time
Find Work: (convert units first!)
Work = ____________
Divide Work by Time:
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