Physics Flashcards
Motion
an object changing position over time, relative to a reference point
Speed
the rate of change in motion
Average Speed
the distance traveled by an object divided by the time taken to go the distance
How is speed calculated?
speed = total distance / total time distance = meters time = seconds
Force
a push or pull exerted by one object on another
What is force measured in?
Newtons
Will motion always occur when a force acts on an object?
No (push on a wall; wall doesn’t move)
Net Force
the combination of all the forces acting on an object
Forces in the same direction…
help us move objects; are added to create a net force
Forces in different directions…
are subtracted
Balanced Forces: What will the net force on an object be?
0 N
Balanced Forces: What will a moving object do when balanced?
It will not change it’s motion.
Balanced Forces: An object not moving…
will not start moving
Unbalanced Forces: What will the net force on an object be?
Not 0 N
Unbalanced Forces: They will produce a change in…
motion (change in speed or direction)
Definition = the tendency of an object to resist changes in its state of motion
Inertia
Definition = when all the forces acting upon an object balance each other, the object will be in this state
Equilibrium
Newton’s First Law of Motion
aka the Law of Inertia
An object in motion will stay in motion, and an object at rest will stay at rest, until acted upon by an outside and unbalanced force
Newton’s Second Law of Motion
A net force acting on an object causes the object to accelerate in the direction of the force. The amount of acceleration is determined by the mass of the object & size of the force
Newton’s Third Law of Motion
For every action, there is an equal and opposite reaction
Work is done when…
a force causes an object to move in the direction of the force
Are work and force the same?
No - just because you apply force does not mean work was done
When is work done?
when the object moves in the direction of the force
How is work calculated?
work = force x distance
force (f) = Newtons
distance (d) = meters
work = joules (J)
Power
the rate at which energy is transferred
How is power calculated and what is it measured in?
measured in watts (W)
power = work / time
Energy
the ability to do work
it is expressed in units of joules (J)
Kinetic Energy (KE)
the energy of motion
What has kinetic energy?
all moving objects
What determines the amount of KE an object has?
how fast it is moving & how much mass it has
How do you calculate kinetic energy?
KE = (mv^2) / 2
(mass x velocity squared) / 2
m = mass
v = velocity/speed
Potential Energy (PE)
the energy of position
What is a type of potential energy?
gravitational potential energy
What determines the amount of gravitational PE an object has?
its weight and its height (how far it has to fall)
How do you calculate gravitational potential energy?
gravitational PE = weight x height
weight = Newtons (N)
height = meters (m)
Mechanical Energy
the total energy of motion & position of an object
What are kinds of mechanical energy?
both kinetic energy & potential energy
Mechanical energy can be…
all KE, all PE, or some of each
How do you calculate mechanical energy?
mechanical energy = PE + KE
What is “the period of a pendulum”?
the time it takes to complete one back and forth swing
How is Thermal Energy formed? Is it Potential or Kinetic?
by the random movement of particles. it is kinetic
How is Chemical Energy formed? Is it Potential or Kinetic?
by the energy of a compound as its atoms are rearranged. it is potential, then kinetic
How is Electrical Energy formed? Is it Potential or Kinetic?
by the energy of moving electrons. it is potential, then kinetic
How is Sound Energy formed? Is it Potential or Kinetic?
caused by an object’s vibrations. it is kinetic
How is Light Energy formed? Is it Potential or Kinetic?
produced by the vibrations of electronically charged particles. it is kinetic
How is Nuclear Energy formed? Is it Potential or Kinetic?
caused by changes in the nucleus of an atom. it is potential, then kinetic
How is Mechanical Energy formed? Is it Potential or Kinetic?
by the KE and PE of an object. it is both kinetic and potential
What is a “closed system”?
a group of objects that transfer energy only to each other
What is a Nonrenewable Energy Source?
an energy resource that cannot be replaced or is replaced much more slowly than it is used. it cannot be made again in a short period of time
What are the Nonrenewable Energy Sources?
- Coal
- Oil (Petroleum)
- Natural Gas
- Uranium
What state of matter are the nonrenewable sources?
Crude Oil (Petroleum) - liquid
Natural Gas / Propane - gas
Coal - solid
Uranium Ore - solid
Why are coal, petroleum, natural gas, and propane considered fossil fuels?
they were formed from the buried remains (fossils) of plants & animals that lived millions of years ago
What is a Renewable Energy Source?
an energy source that is naturally replaced more quickly than it is used. it can be replenished naturally in a short period of time
What are the Renewable Energy Sources?
- Biomass (trash, trees, etc.)
- Hydropower (water)
- Geothermal
- Solar
- Wind
In 2011, what % of U.S. electricity was generated from renewable sources?
13%
Why don’t we use more renewable energy?
- more expensive to produce & use
- resources are in remote areas so it is a challenge to build power lines to cities
- they are not always available (cloudy days, calm days, drought)
- safety concerns regarding nuclear failure
What is an “energy resource”?
a natural resource that can be converted into other forms of energy to do work
Advantages of Fossil Fuels
- provide a large amount of thermal energy per unit of mass
- are easy to get & transport
- can be used to generate electricity & to make products such as plastic
Disadvantages of Fossil Fuels
- are nonrenewable
- produce smog
- release substances that can cause acid precipitation
- create a risk of oil spills
Advantages of Nuclear Energy
- is a very concentrated form of energy
* does not produce air pollution
Disadvantages of Nuclear Energy
- produces radioactive waste
* is nonrenewable
Advantages of Solar Energy
- is an almost limitless source of energy
* does not produce pollution
Disadvantages of Solar Energy
- is expensive to use for large-scale energy production
* is practical only in sunny areas
Advantages of Hydropower Energy
- is renewable
* does not produce air pollution
Disadvantages of Hydropower Energy
- requires dams, which disrupt a river’s ecosystem
* is available only where there are rivers
Advantages of Wind Energy
- is renewable
- is relatively inexpensive to generate
- does not produce air pollution
Disadvantages of Wind Energy
• is practical only in windy areas
Advantages of Geothermal Energy
- is an almost limitless source of energy
* power plants require little land
Disadvantages of Geothermal Energy
- is practical only in areas near hot spots
* produces wastewater, which can damage soil
Advantages of Biomass Energy
- is renewable
* is inexpensive
Disadvantages of Biomass Energy
- requires large areas of farmland
* produces smoke
What are Simple Machines?
a simple machine is a machine with few or no moving parts.
What do Simple Machines do?
simple machines make work easier (work is done when a force is applied through a distance)
The work DONE ON a machine is called the ___
work input
The work DONE ON a machine is called the work input, and this work is caused by an ___
input force
The work a machine does is CAUSED by the ___
output force
The work a machine does is CAUSED by the output force and is called ___
work output
What is Mechanical Advantage?
the benefit gained by using machines
A good machine puts out ___ than is ___!
1) more force
2) put into it
Types of Simple Machines: What are Gears?
two toothed wheels that fit together either directly or through a chain or belt
examples of Gears
clock, bicycle gear chains, drill
Types of Simple Machines: What is an Inclined Plane?
a sloping surface such as a ramp
An inclined plane can alter the ___ and ___ involved in doing work.
effort & distance
The trade-off of an inclined plane is that an object must be moved a ___ distance than if lifted straight up.
longer
examples of Inclined Planes
staircase, ramp
Types of Simple Machines: What is a Lever?
a straight rod or board that pivots a point known as a fulcrum
A fulcrum can be moved depending on the ___ of the object.
weight
Pushing down on one end of the ___ results in the ___ motion of the ___ end of the fulcrum.
1) lever
2) upward
3) opposite
examples of Levers
door on hinges, seesaw, hammer, bottle opener
Types of Simple Machines: What is a Pulley?
a wheel that usually has a groove around the outside edge
The groove is for a ___ or ___ to move around the pulley.
rope or belt
By pulling ___ on the rope it can ___ an object that is ___ to the rope.
1) down
2) lift
3) attached
Work is made ___ because pulling down on the rope is made easier due to ___.
1) easier
2) gravity
examples of Pulleys
flagpole, ski lift
Types of Simple Machines: What is a Screw?
an INCLINED PLANE wrapped around a shaft or cylinder
The inclined plane allows the screw to ___ itself or to move an object or material surrounding it when ___.
1) move
2) rotated
examples of Screws
bolt, jar lid
Types of Simple Machines: What is a Wedge?
2 inclined planes joined back to back
Wedges are used to ___ things.
split
examples of Wedges
axe, zipper, knife
Types of Simple Machines: What is a Wheel and Axle?
consists of 2 wheels of different sizes that rotate together
When the ___ wheel (axle) is turned the ___ wheel moves a greater distance, and ___ force is needed to move it.
1) small
2) larger
3) less
examples of the Wheel & Axle
door knob, car/wagon wheels
Types of Simple Machines: What are Compound Machines?
2 or more simple machines working together to make work easier
examples of Compound Machines
wheelbarrow, can opener, stapler
What is Mechanical Advantage?
the benefit gained by using machines. it compares the INPUT FORCE with the OUTPUT FORCE
What is the formula for Mechanical Advantage?
Mechanical Advantage = Output Force / Input Force
