Transcript Energy Powerpoint

What happens to the gravitation
force on an object as it gets closer
to another object?
Agenda for Monday Nov 10th
1. Quiz
2. Energy Notes
Nature of Energy
• Energy is all around!
– Sound
– Light
– Wind
• Living organisms need energy
Nature of energy
• Energy is involved when
– A bird flies
– A bomb explodes
– Rain falls
– Electricity flows through a wire
Law of Conservation of Energy
• Energy cannot be created or destroyed
– It can only be converted from one form to another
• 1905, Albert Einstein said mass and energy
can be converted into each other
– Matter is destroyed, energy is created and vice
versa
– E = mc2
Nature of energy
• Energy is the ability to do work
– If something does work (exerts a force over a
distance) it uses energy
• Direct connection between energy and work
– measured in the same unit: Joules (J)
Forms of Energy
• 5 main categories
– Heat
– Chemical
– Electromagnetic
– Nuclear
– Mechanical
1. Heat Energy
• Internal motion of the atoms
– Moving particles produce heat
• Heat energy can be produced by friction
• Heat energy causes changes in temp. and
phase of any form of matter
What is the law of conservation of
energy?
Agenda for Tuesday Nov 11th
1. Finish notes
2. Problems on GE/KE
2. Chemical Energy
• Energy that is available for release from
chemical reactions.
• The chemical bonds in a matchstick store
energy that is transformed into thermal
energy when the match is struck.
• Fuel and food
Examples of Chemical Energy
3. Electromagnetic
Energy
• Gamma rays, x-rays, ultraviolet rays,
visible light, infrared rays, microwave
and radio bands
• Power lines carry electromagnetic
energy in the form of electricity
• Light - each color (ROYGBIV) is a
different amount of energy
4. Nuclear Energy
• Nucleus of an atom is the source of nuclear
energy
• SUN
– Fission & Fusion
5. Mechanical Energy
• Energy due to a object’s motion (kinetic)
or position (potential)
• When work is done to an object, it acquires
energy
• When you kick a football, you give mechanical
energy to the football to make it move
Energy Conversion
• Energy can be changed from one form to another
– Changes in the form of energy are called energy
conversions
• All energy forms can be converted to other forms
– Sun through solar cells to electricity
– Plants take sun energy to sugars (electromagnetic to
chemical)
States of Energy
• Most common energy conversion is between
potential and kinetic energy
• All forms of energy can be in either of 2 states
– Potential
– Kinetic
Kinetic Energy
• Kinetic Energy – energy of motion
– Depends on mass and velocity
– Faster an object moves, more kinetic energy it has
– Greater the mass, more kinetic energy it has
• KE – 1/2mv2
• What has a greater affect of kinetic energy, mass
or velocity? Why?
Potential Energy
• Potential energy – stored energy
– Fuel, nucleus, food
– Stored because of the work done on it:
•
•
•
•
Stretching a rubber band
Winding a watch
Pulling back on a bow’s arrow
Lifting a brick high in the air
• Energy that is stored due to being stretched or
compressed is elastic potential energy
Gravitational Potential Energy
• Potential energy that is dependent on height
– Waterfall
– Suspension Bridge
– Falling snowflake
• GPE = weight x height
Or
• GPE = mgh
Gravitational Potential Energy
• If you stand on a 3 meter diving board, you have 3
times the GPE than you had on a 1 meter diving board
Kinetic - Potential Energy Conversions
• Roller Coaster
– Mechanical energy brings them to the top
– This gives them great potential energy
– Conversion between potential to kinetic energy
powers cars through the entire ride
• At the point of max PE, the car has minimum KE
Kinetic - Potential Energy Conversions
• As a baseball
player throws the
ball into the air,
various energy
conversions take
place
Which has more gravitational
potential energy: a ball on a 5 m
cliff or a ball on a 10 m cliff? Why?
Agenda for Wednesday Nov 12th
1. Bouncing ball lab
All late work due Wednesday Nov 19th
Where is the most kinetic energy?
Most potential energy?
B
D
A
C
Agenda for Thursday Nov 13th
1. KE/GPE Problem set
Equations for Energy
Practice Problems
1. A 800g ball is lifted 20 cm. Calculate the
potential energy it gains.
2. A man climbs on to a wall that is 3.6m high
and gains 2268J of potential energy. What is
the mass of the man?
1. Determine the kinetic energy of a 625-kg
roller coaster car that is moving with a speed of
18.3 m/s.
2. What is the kinetic energy of a 0.50 kg ball
travelling at a speed of 120 m/s ?