Download Homework#6 7.p.2

Review:
7.P.2.1
Mechanical energy is the energy possessed by an object due to its motion or its stored energy of position. Mechanical
energy can be either kinetic (energy of motion) or potential (energy of position). An object that possesses mechanical
energy is able to do work. Mechanical energy is the form involved in the operation of simple machines.
7.P.2.2
Objects that have potential energy do not use their energy until they move. That is why it is called “potential” energy.
Potential means that something is capable of becoming active. Any object that can move to a lower place has the
potential to do work on the way down, such as a marble rolling down a driveway. Objects also store energy in motion. A
moving mass can certainly exert forces, as you would quickly observe if someone ran into you during a basketball game.
Energy of motion is called kinetic energy. Energy appears in different forms, such as motion and heat. Energy can travel
in different forms, such as light, sound, or electricity. The workings of the universe plus all of present day technology can
be viewed from the perspective of energy flowing from one place to another and changing back and forth from one form
to another.
Guiding Questions:
1. How does height affect the potential energy of an object?
2. How does speed affect the kinetic energy of an object?
3. How can the total sum of mechanical energy in a system be determined using potential and kinetic
energy?
4. How can a force change the speed of an object?
Calculate the speed for: (Show your work)
#1:____________
#2:____________
#3:____________
5.
Review:
7.P.2.1
Mechanical energy is the energy possessed by an object due to its motion or its stored energy of position. Mechanical
energy can be either kinetic (energy of motion) or potential (energy of position). An object that possesses mechanical
energy is able to do work. Mechanical energy is the form involved in the operation of simple machines.
7.P.2.2
Objects that have potential energy do not use their energy until they move. That is why it is called “potential” energy.
Potential means that something is capable of becoming active. Any object that can move to a lower place has the
potential to do work on the way down, such as a marble rolling down a driveway. Objects also store energy in motion. A
moving mass can certainly exert forces, as you would quickly observe if someone ran into you during a basketball game.
Energy of motion is called kinetic energy. Energy appears in different forms, such as motion and heat. Energy can travel
in different forms, such as light, sound, or electricity. The workings of the universe plus all of present day technology can
be viewed from the perspective of energy flowing from one place to another and changing back and forth from one form
to another.
Guiding Questions:
1. How does height affect the potential energy of an object?
2. How does speed affect the kinetic energy of an object?
3. How can the total sum of mechanical energy in a system be determined using potential and kinetic
energy?
4. How can a force change the speed of an object?
Calculate the speed for: (Show your work)
#1:____________
#2:____________
#3:____________
5.
7.P.2.3
Energy can be transferred from one system to another (or from a system to its environment) in different ways:
1. Thermally, when a warmer object is in contact with a cooler one
2. Mechanically, when two objects push or pull on each other over a distance
3. Electrically, when an electrical source such as a battery or generator is connected in a complete circuit to an
electrical device
4. By electromagnetic waves
Energy is one of the fundamental building blocks of our universe. Energy can change from one form to another, although
in the process some energy is always converted to heat. Some systems transform energy with less loss of heat than
others. Electrical energy can be produced from a variety of energy sources and can be transformed into almost any
other form of energy. Batteries store energy and transfer energy to components in a circuit. In the battery the energy
comes from chemical reactions. Electricity is important because we can use it to make so many things work (electrical
energy). For example, a bulb converts electrical energy into light energy and a speaker converts it into sound energy.
The electrical energy generated by windmills, waterfalls and power plants is actually a secondary source of energy. To
produce electricity, a heat source is needed to create the conditions in which electrical currents form. In effect, the
primary source of electrical energy is the heat generated by burning fossil fuels, water power, and wind power. A natural
form of electrical energy can be seen in the lightning that appears during storms. Solar energy, water, and wind power
are sources of green energy – meaning they do not pollute the environment.
7.P.2.4
A machine is a device that makes work easier by changing the size or direction of a force. When you use a machine, you
do the work on the machine, and the machine does the work on something else. Mechanical advantage is the number of
times the machine multiplies force. Ideal Mechanical Advantage (IMA) is what is desired of a machine, where Actual
Mechanical Advantage (AMA) is what the machine actually does. A lever is a simple machine that has a bar that pivots at
a fixed point called a fulcrum. A pulley is a simple machine that consists of a wheel over which a rope, chain, or wire
passes. A simple machine that consists of two circular objects of different sizes is known as a wheel and axle. The
mechanical advantage of a wheel and axle is the radius of the wheel divided by the radius of the axle. A simple machine
that is a straight, slanted surface and facilitates the raising of loads is an inclined plane. A compound machine consists of
two or more simple machines put together. In fact, most machines are compound machines. Some examples are a pair
of scissors and a bicycle.