Transcript Document

ENERGY & POWER
I. Energy = the ability to do
work.
A. Work and Energy:are related, we
give energy to an object by doing
work on the object.
B. Measuring Energy: Because work
is the transfer of energy, we can
measure energy by measuring the
work done.
 For example if a boat does
5,000 Newton’s of work, the
engine of the boat put out
5,000 N-m’s of energy.
One Newton meter is = to a
Joule (J)
 So to find out how much
energy is needed to do
something we use the formula
for work.
II.Kinetic Energy: is the energy
of motion.
A. If you stop a moving object you can
feel it’s Kinetic Energy.
1. Kinetic Energy depends on two
things.
 Mass & Speed of the object.
More Kinetic Energy
100km/hr
100km/hr
III.Calculating Kinetic Energy:
KE=1/2mv2 answer is in Joules.
mass
velocity
Example: A girl has a mass of 40 kg
skates around a rink at 12m/s. What is her
Kinetic energy?
1.A boy has a mass of 120 kg runs at a
speed of 4 m/s. What is his KE?
2.A man has a mass of 100 kg walks at
a speed of 2 m/s. What is his KE?
3. A baseball with a mass of 0.08 kg is
thrown at a speed of 20 m/s. What is
the KE of the baseball?
4. A soccer ball with a mass of 2 kg is
kicked at a speed of 5 m/s. What is
the KE of the soccer ball?
IV.Potential Energy: Is energy
due to an objects position.
A. Calculating Potential Energy: Is work
done or Force X Distance = Joules
1. Example: If a boy carries a 70 n bowling
ball up a flight of 20 m high stairs. What is
the balling ball PE?
Answer: 70 n X 20 m = 1400 J
B.Law of Conservation of
Energy: States that energy
cannot be created or
destroyed. It can change
from one form to another.
But the total amount of
energy remains the same.
{EXCEPT SOME IS LOST
DUE TO FRICTION}
C.Friction Wastes Energy:
1. The lower the friction the less energy wasted.
2. The less energy wasted the faster you go.
3. The less energy wasted the more PE converted
to KE.
PE
PE & KE
PE if
Stopped
V. Forms of Energy
1. Mechanical: energy an object has from its motion.
2. Internal: energy from all the particles of an object.
3. Electrical: electricity
4. Chemical: energy from an objects
position and its form of PE.
5. Radiant: energy in the form of a wave the
sun
6. Nuclear: energy released from splitting or
combining atoms.
A.Power: is the rate at which work is
done.
1. Power = work/time it’s the rate at which
energy is used.
 Example: If a person used 1200 J’s of energy in
10 minutes how much power does that person
have?
Answer: 1200 J / 10 minutes = 120 J/m
Some times we convert minutes to seconds for
example 10 minutes = 600 seconds.10 X 60.
2. 1 Joule per second is equal to a watt (W)
3. Power is measured in watts.
1- Chemical Energy: Energy from an
objects position. (Potential Energy)
2- Electrical Energy: Energy that flows
through a wire (Kinetic Energy)
3- Energy: The ability to do work.
4- Internal Energy: Energy to the particles
that make it up.
5- Joule: Metric Unit for energy.
6- Kinetic Energy: Energy because the
object is moving.
7- Law of Conservation of Energy:
Energy cannot be created or destroyed.
Energy changes from on form to another.
8- Mechanical Energy: Energy an object
has from its motion.
9- Nuclear Energy: Form of Potential
energy the splitting of atoms
10- Potential Energy: Energy due to an
objects position. We give objects energy
by doing work on them.
11- Power: The rate at which work is
done.
12- Radiant Energy: Energy from the sun
in the form of a wave.
13- Watt: Metric unit for power.
14-If the rock's potential energy is100 J,
the hill is _________ high.
5N
A
15-At point C, the rock's potential
energy will be __________ .
B
16-The rock's kinetic energy at point
A is __________.
17-At point B, some of the rock's potential
energy will be changed to.
________________________________
18-The rock's potential energy at point
A is __________ than it's kinetic energy.
C