Transcript Kinetic energy - Cobb Learning

EQ – How is life affected by energy?
• EQ – How is life affected by energy?
• S8CS2 (Habits of Mind) & S8CS8 (Nature of Science)
• S8P2. Students will be familiar with the forms and
transformations of energy.
• a. Explain energy transformation in terms of the Law of
Conservation of Energy.
• b. Explain the relationship between potential and kinetic energy.
• c. Compare and contrast the different forms of energy (heat,
light, electricity, mechanical motion, sound) and their
characteristics.
• d. Describe how heat can be transferred through matter by the
collisions of atoms (conduction) or through space (radiation). In
a liquid or gas, currents will facilitate the transfer of heat
(convection).
Energy
• Energy is the ability to do work.
Kinetic energy
-the energy of motion.
KE depends on both mass and
speed. The more mass an
object has the more kinetic
energy it has. The faster
something is moving, the more
kinetic energy it has.
• Changing the velocity
(the speed in a specific
direction) of an object
will have a greater
effect than changing
its mass. Why? (KE= ½
x M x V²)
• Speed has a greater effect on
kinetic energy than mass does.
Why? KE= ½ x M x V²
• M= mass
• V = speed
Calculate
• What is the kinetic energy of a girl
who has a mass of 40 kg and a
velocity of 3 m/s?
• What do you know: mass = 40 kg,
velocity = 3 m/s
• Write the formula: KE = ½ mv2
• Substitute into the formula:
KE = ½ x 40 kg x (3 m/s)2
KE = ½ x 40 kg x 9 m2/s2
= 360 kg x m2/ 2 s2
= 180 kg x m2/s2
Or
KE = 180 J
Solving Velocity
• Velocity = distance/time
• Example: V= 50m/32s
• = 1.56 m/s
A hockey player on the ice
has kinetic energy
-stored energy.
The ball has
Potential to
move.
Potential energy can be
increased by:
• Increasing height
• Increasing mass
Three Types of Potential Energy
• Elastic – energy stored in objects that
can be stretched
• Chemical – energy stored within
chemical substances (i.e. coal)
• Gravitational – energy due to the height
of an object (PE= M x 9.8 m/s/s
[acceleration due to gravity] x height)
Calculating PE
•
•
•
•
PE = mgh
where PE = Energy (in Joules)
m = mass (in kilograms)
g = gravitational acceleration of the
earth (9.8 m/sec2)
• h = height above earth's surface (in
meters)
• What is the gravitational
potential energy of a girl who
has a mass of 40 kg and is
standing on the edge of a
diving board that is 5 m above
the water?
• What do you know?
–Mass = 40 kg, gravitational
acceleration = 9.8 m/s2, height = 5
m
• What do you want to find out? GPE
• Write the formula: GPE = mph
• Substitute into the formula: 40 kg x
9.8m/s2 x 5 m
• GPE = 1960 kg
2
2
m /s
• Unit of energy is Joules or J
• Answer: 1960 J
A rubber band has potential to be
shot. (elastic energy)
What other things can you think of
that have potential energy?
A waterfall has both kinetic
and potential energy.
The water at the top of the waterfall
has stored potential energy.
Once the water leaves the top of the
waterfall, the potential energy is
changed into kinetic energy.
Law of Conservation of Energy
• Energy cannot be created or
destroyed; it may be changed
from one form to another, but
the total amount of energy
never changes.
Forms of Energy
• Chemical – holds atoms and molecules together; released by
chemical reactions
• Electrical – movement of electrons through matter; electricity
• Heat – vibration of particles within matter; faster = more heat
• Light – energy carried by light; electromagnetic spectrum
• Mechanical – energy of moving things
• Sound – vibration of air molecules that causes movement of tiny
bones in your ear to send a message to your brain in order for
you to hear; vibrates all forms of matter
• Nuclear – holds protons and neutrons together in the nuclei of
atoms; powers the sun and nuclear power plants
More info:
http://www.fi.edu/guide/hughes/energy_us.html