Chapter 13 Flashcards
W=
F(d)
-the transfer of energy to an object by the application of a force that causes the object to move in the direction of force
Work
Work is measured in ______.
Joules
1N(m)=
1J
1J=
1kg(m2/s2)
-a quantity that measures the rate at which work is done or energy is transformed
Power
Power=
work/time
Power is measured in _____.
watts
____ multiply and redirect force.
Machines
-a quantity that expresses how much a machine multiplies force or distance
Mechanical Advantage
When lifting a box straight up, a mover applies a ___force over a ____ distance.
Large
Short
Using a ramp to lift the box, the mover applies a ____ force over a ____ area.
Smaller
Longer
M.A.=
output force/input force
or
input distance/ output distance
-one of the six basic types of machines, which are the basis for all other forms of machines
Simple Machine
Simple machines are split into two families. What are they?
Lever family
Incline plane family
The lever family includes the _____, _____, and the _____.
Simple lever
Pulled
Wheel and axle
The incline plane family include the _____, _____, and ______.
Simple incline plane
Wedge
Screw
Levers are divided into ___.
Three classes
All _______ have a fulcrum located between the points of application of the input and output forces. See-saw.
First-class levers
In _____ the fulcrum is at one end of the arm and the input force is applied to the other end. Ex. Wheelbarrow
Second class lever
____ multiply distance rather than force. As a result, they have less mechanical advantage than 1. The human body contains many of these.
Third-class levers
What are modified levers?
Pulleys
A _____ is a lever or pulley connected to a shaft.
Wheel and axle
What do inclined planes do?
They multiply and redirect force.
What is a modified inclined plane?
A wedge
What is an inclined plane wrapped around a cylinder?
A screw
-machines made of more than one simple machine
Compound Machine
What is the ability to do work?
Energy
What is energy measured in?
Joules
What do you expel work to do?
Pull a sling on a sling shot back.
-the energy that an object has because of its position, shape, or condition
Potential energy
-the energy stored in any type of compressed or stretched elastic material
Elastic Potential Energy
-the energy that could potentially do work due to an object’s position above ground
Gravitational Potential Energy
What depends on both mass and height?
Gravitational potential energy
PE=
mgh
What can be relative or become important when calculating gravitational potential energy?
Height
What is the energy of an object due to the object’s position?
Kinetic energy
What depends on mass and speed?
Kinetic Energy
KE=
1/2(mv2)
What does kinetic energy depend on most?
Speed more than mass
-the amount of work an object can do because of the object’s kinetic and potential energy
Mechanical Energy
ME=
PE+KE
What things have kinetic energy?
Atoms and molecules
Chemical reactions involve _______.
Potential energy
Living things get energy from the ___.
Sun
Where does the sun get energy from?
Nuclear reactions
What is a form of energy?
Electricity
What can become kinetic energy?
Potential energy
Give an example of potential energy.
Almost all the energy of a roller coaster car at the top of a tall hill is potential energy
When and how does the potential energy change to kinetic energy in a coaster car?
It gradually changes to kinetic energy as a car accelerates downhill
___ energy can become ____ energy.
Kinetic energy
Potential energy
When does kinetic energy convert to potential energy in a roller coaster?
As the car hits the lowest point and begins to climb another hill
What is energy lost to as object’s travel?
Friction and vibration
Will the roller coaster car be able to climb a hill as tall as the first hill due to these transformations of energy?
No
____ energy can be changed to _____ energy.
Mechanical
Non mechanical
What explains the flight of a baseball?
Energy transformations
When a ball is hit, the ball does what?
It keeps rising until all the kinetic energy is gone.
What is all of the ball’s energy when it is at its highest point?
Potential energy
What happens as the ball falls?
All of its potential energy changes back to kinetic energy
-energy cannot be created or destroyed
The Law of Conservation of energy
Does energy appear or disappear?
No
What describes energy conservation?
Thermodynamics
Accounting for all of the energy in a system can be ____.
Complicated
What makes accounting for all the energy easier?
Studying a small, defined area
What are these defined areas called?
Systems
Systems can be ____ or ______.
Open
Closed
Which systems exchange energy with the space that surrounds them?
Opened systems
When would a system be considered closed?
If the flow of energy into and out of a system is small enough to be ignored
Is all work done by machines useful?
Haha no
What is the measure of how much useful work is done?
The efficiency of a machine
Efficiency=
Useful work output/work input
What is efficiency usually expressed as?
A percentage
What machines are impossible?
Perpetual motion machines
REVIEW MATH SKILLS PROBLEM ON PAGE 460
Machines need _____.
Energy input
COMPLETE SECTION 4 REVIEW, PG. 461, #1-9
PLEASE DO IT ANNA
What results from energy transfer?
The feeling associated with temperature difference
What indicates an energy transfer?
Temperature changes
