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Mechanical Energy
the energy due to the position of something or the movement of something (potential energy or kinetic energy)
law of conservation of energy
Energy may be transferred from one object to another but it is never created or destroyed.
elastic potential energy in a bow and arrow
You change the shape of the bow and give it elastic potential energy. When you let the bow go, it returns to its original shape. The energy is transformed to kinetic energy and transferred to the arrow.
potential energy in a roller coaster
The potential energy of the cars at the top of a roller coaster is transformed into kinetic energy when the cars go down the hill.
potential energy and kinetic energy on a roller coaster
PE + KE are always the same number, but the amount of PE and the amount of KE change as the roller coaster car goes up and down.
a boulder can just sit on top of a mountain and have lots of energy (potential)
This boulder (big rock) has a lot of potential energy because it has a lot of mass and it is high off the ground. It is awful to think about what would happen if it fell!
a skateboarder enjoying kinetic energy
The skateboarder is converting potential energy to kinetic energy as he goes down the hill.
Potential Energy
(mass) x (g) x (height)
energy transformation
A change from one form of energy to another is called_______
Joule (J)
SI unit Work and Energy
gravitational potential energy
an icicle hanging from a rooftop
elastic potential energy
a stretched bungee cord
Transformation of Energy in a Bow and Arrow
You change the shape of the bow and give it elastic potential energy. When you let the bow go, it returns to its original shape. The energy is transformed in the bow is transformed …
Transformation of Energy in a Roller Coaster
The potential energy of the cars at the top of a roller coaster is transformed into kinetic energy when the cars go down the hill.
Total Mechanical Energy on a Roller Coaster
PE + KE are always the same number, but the amount of PE and the amount of KE change as the roller coaster car goes up and down.
Gravitational Potential Energy of a Boulder
This boulder (big rock) has a lot of potential energy because it has a lot of mass and it is high off the ground. Think about how much work it could do if we …
Energy Transformation of a Skateboarder
The skateboarder is converting potential energy to kinetic energy as he goes down the hill. Think of why.
thermal energy
a hot coffee mug
Solar energy
Energy we get from the sun
electrical energy
a power line
kinetuc energy
the energy an object has due to its motion
law of conservation
principle that the total momentum stays the SAME, never changes, just transfers, unless an unbalanced force acts upon it(friction, heat reduce it)
Electromagnets
A type of magnet whose magnetic field is produced by the flow of electric current.
generators
produces an electric current when a coil of wire wrapped around an iron core is rotated near a magnet
simple electric motors
changes electrical energy to mechanical energy because an electromagnet rotates between pole of a magnet
light energy
electrical energy transformed in an electric circuit if a light bulb is added to the circuit
sound energy
a clap of thunder
mechanical motion
electrical energy can be transformed into the energy of mechanical motion if a fan is added to the circuit
Conduction
the direct transfer of heat or sound from one substance to another substance that it is touching
convection
the process whereby heat is transferred by the mass movement of molecules from one place to the other
energy that is radiated or transmitted in the form of rays or waves or particles
spring scale
used to measure force in SI units called newtons (N)
work
a force acting upon an object to cause a displacement. (key words: force, displacement, and cause)
lever
a rigid bar or board that is free to move around a fixed point called a fulcrum
pulley
a grooved wheel with a rope running along the groove
Inclined Plane
A flat surface set at an angle or an incline with no moving parts that is able to lift objects by pushing or pulling the load.
wheels and axles
consist of two circular objects: a central shaft insert into a circular device
complex machines
consist of two or more simple machines
Everyday Meaning: labor, task, or duty
Scientific vs. Everyday meaning of the word 'Work.'
Formula for Work Energy
Work = F d cos Ɵ
Positive Work Energy
Work is positive when the force is in the same direction as the displacement.
Negative Work Energy
Work is negative when the force is in the direction opposite to the displacement.
You lift a box off the ground.
The work done when you lift a box is positive because the force is upwards, in the same direction as the displacement.
A librarian pulls a cart of books along a hallway.
The work done on the cart is positive because the force is forwards, in the same direction as the displacement.
Power
(physics) the rate of doing work
Explain how energy, time and power are related.
Power is the rate at which energy is transferred. In other words, power is the energy transferred in a given time interval.
Watt
A measure of power equal to one joule of work per second.
When is work achieved?
A force does work on an object if a component of the force is parallel to the displacement of the object.
Spring Constant
A parameter that is a measure of a spring's resistance to being compressed or stretched.
Chemical Potential Energy
Energy stored in chemical bonds.
friction
a contact force; type of force between two touching surfaces
Non-mechanical Energy
Energy that does not involve the large-scale motion or position of objects in a system.
Work = F d cos Ɵ
The magnitude of the component of the force that does work is 34.0 N done on a crate being pulled 4.50 meters at an angle of 37.0° from the horizontal.
ME (initial) = ME(final)
A 2.50 kg stapler falls from a height of 2.0 meters. Just before hitting the ground, what will it's kinetic energy be? (Disregard air resistance)
Who demonstrated more power?
Both Mr. Bunsen and Mr. Burner performed the same work because they applied the same force up the same distance.
Power = Work (J) / Δtime (s)
What is the average power supplied by a 75.0 kg person running up a flight of stairs rising vertically 4.0 meters in 5.5 seconds?