Describing Energy

Describing Energy

Kinetic and Potential Energy

• Kinetic energy is energy in motion.

• Potential energy is stored energy.

• When a resting object begins to move it is converted from potential energy to kinetic energy.

• The higher an object is, the more potential energy it has. Potential energy can be found in a roller coaster at the top of a hump, a rubber band being stretched, a battery that is not being used or a ball in a baseball players hand waiting to be thrown.

• Kinetic energy can be found in a ball rolling down a hill, a roller coaster flying down a hump, a toy moving with battery power and more.

Multiple Choice

A diagram of a pendulum is shown below. The pendulum is released from Position 1. At which two positions will the pendulum’s potential equal its kinetic energy?

• 1 and 2

• 2 and 4

• 3 and 4

• 4 and 5

Multiple Choice

Which of these best shows a change from potential to kinetic energy?

• Water flowing over a tall cliff

• A rubber band being stretched

• Electricity making a bulb light up

• A stone lying on top of a mountain

Multiple Choice

A truck is parked at the bottom of a hill. It moves from the bottom of a hill and parks at the top. Compared to when it was parked at the bottom of the hill at its new position, the truck now has -

• more potential energy.

• more kinetic energy

• less potential energy

• less kinetic energy

Multiple Choice

The illustration shows a rollercoaster and indicates four different positions the car might be at as it moves along the track. At which point in the rollercoaster's journey is its potential energy the greatest?

• W

• X

• Y

• Z

Multiple Choice

When would a skateboarder have the most potential energy?

• While rolling down the ramp

• While moving up the ramp

• At the bottom of the ramp

• At the top of the ramp

Thermal Energy Transfer: Conduction, Convection, and Radiation

• Conduction is the transfer of energy from one molecule to another by direct contact. This can occur when a pot comes in contact with, the hot surface of a stove.

• Convection is the movement of heat by a fluid such as water or air. The liquid or gas moves from one location to another, transferring heat along with it using convection currents.

• Radiation is the transfer of heat by electromagnetic waves. Standing in the sun, you are warmed by the electromagnetic waves that travels from the sun to Earth. Light bulbs, irons, and toasters also transfer heat via radiation.

Thermal Energy Transfer

• Thermal energy can be measured using tools such as hot plates, beakers and thermometers.

• Conduction takes place in solids, liquids, and gases, but works best in materials that have simple molecules that are located close to each other. For example, metal or glass are better conductors than wood or plastic.

• Conduction can be seen when a hand touches a hot stove and gets burned or when a hot iron touches a shirt to remove the wrinkles.

Forms of Energy

• There are many different forms of energy, such as chemical energy (energy stored in bonds between atoms), electrical energy (energy of electric currents), and light energy (energy of electromagnetic waves).

• Chemical energy is the energy that is stored within atoms’ bonds.  A battery contains chemical energy, which can be transformed to electrical energy, for example to light a flashlight.

Multiple Choice

Four steel blocks were heated to different temperatures and stacked together as shown. In which direction will heat be transferred by conduction?

• From Sample 4 to Sample 1

• From Sample 2 to Sample 3

• From Sample 2 to Sample 4

• From Sample 3 to Sample 2

Multiple Choice

When an egg is boiled in a pot of water on the stove, there is more than one kind of heat transfer. Heat is transferred from the stove to the pot directly since they are physically touching. Heat is also transferred from the pot to the egg, carried through the water. What two kinds of heat transfer are represented?

• Stove → Pot = radiation, Pot → Egg = conduction

• Stove → Pot = conduction, Pot → Egg = radiation

• Stove → Pot = convection, Pot → Egg = conduction

• Stove → Pot = conduction, Pot → Egg = convection

Multiple Choice

Which of the following sets of tools would be most useful in an experiment measuring the rate of transfer of thermal energy in four different liquids?

• Triple-beam balance, beakers, metric ruler

• Hot plate, beakers, thermometers

• Microscope, funnel, metric ruler

• pH meter, test tubes, forceps

Multiple Choice

Water at 34º C was placed into containers made of four different materials. An initial temperature was taken, and a final temperature was taken after 10 minutes. Which container allowed the most transfer of thermal energy from the water to the environment?

• Glass

• Wood

• Paper

• Plastic

Multiple Choice

Which of the following is an example of conduction?

• Solar energy warming a room

• Heat rising from the coils of a stove

• Hot air drying a wet towel

• Heat moving from a clothes iron to a shirt

Multiple Choice

A lamp that plugs into a wall socket draws energy which flows through a thin wire in the bulb causing it to glow. What energy transformations are taking place?

• Chemical → Light → Electrical

• Mechanical → Sound → Light

• Thermal → Solar → Electrical

• Electrical → Thermal → Light

Multiple Choice

Which of the following shows the correct order of the energy transformations that occur when green plants produce their food from the Sun's energy?

• Chemical → Thermal

• Light → Chemical

• Thermal → Light

• Chemical → Electrical

Multiple Choice

Which of the following shows the energy transformation that occurs when solar panels are used to heat a building?

• Light → Thermal

• Chemical → Electrical

• Thermal → Chemical

• Light → Mechanical

Multiple Choice

The picture shows a light bulb attached to a hand generator. What energy transformation occurs as the handle of the generator is turned?

• Thermal --> solar --> light

• Solar --> light --> electrical

• Mechanical --> electrical --> light

• Electrical --> mechanical --> light

Multiple Choice

The picture shows a microwave oven. As a microwave oven is operated, electrical energy is transformed into all of the following types of energy EXCEPT -

• solar

• light

• mechanical

• thermal