Chapter 5
Energy
Energy and Work
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Energy – the ability to cause change.
Kinetic energy – energy in the form of motion.
Potential energy – stored energy.
Work – the transfer of energy through motion.
– Work = Force x Distance
– W = FD
– Units = Joules (Newtons x meters)
Conservation of Energy
• Mechanical energy – the total amount of
kinetic and potential energy in a system.
• Law of conservation of energy – states that
energy can change form but it cannot be
created or destroyed under ordinary
conditions.
Human Energy
• Calorie – a unit used by nutritionists to
measure how much energy we get from
specific foods.
– 1 calorie ( = 1 kilocalorie) – 4180 Joules.
– Each gram of fat supplies 9 calories of energy.
Temperature and Heat
• Temperature – a measure of the average kinetic
energy of the particles in a sample of matter.
• Thermal energy – is the total energy of the
particles in a material.
• Heat – the thermal (or internal) energy that flows
from something with a higher temperature to
something with a lower temperature. (i.e. heat is
energy transferred between objects at different
temperatures.
Thermal Pollution
• Thermal pollution – when waste heat
significantly changes the temperature of the
environment.
Measuring Thermal Energy
• Specific heat – amount of energy it takes to raise
the temperature of 1kg of a substance by 1o C.
• Thermal Energy Equation
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Q = mc∆T
Q is change in thermal energy
m is mass
c is specific heat
∆ is the final temp. – the initial temp.