The Nature and Conservation of Energy

1 calorie

= 4,184 J

Thermal energy is... A. Kinetic. B. Potential. C. Both kinetic and potential. D. Neither kinetic nor potential.

A

Joule

Joule= kg x (m/s)^2

Energy

The ability to do work or cause change

Thermal Energy

source: fire, warm objects uses: to heat things

Chemical Energy

source: flood, gasoline uses: power, energy for living things

Radiant Energy

source: light bulbs, sun, fire uses: to see, power source, move energy

Electrical Energy

source: power plants, batteries uses: power objects, move energy

Nuclear Energy

source: the nucleus of an atom uses: power source, medicine

Sound Energy

source: tv, radio uses: communications

Potential Energy

stored energy

Nuclear Fusion

the combining of small nuclei (this is what powers the sun)

Practice Problems: A crane lifts a beam to a height of 30 meters, giving it a potential energy of 108,486 J. What is the mass of the beam?

108,486 J= m(9.8)(30) m=369 kg

An object that has kinetic energy must be... A. Lifted above earth's surface. B. In motion. C. At rest. D. None of the above.

B

Energy is... A. When the surfaces of two objects rub against each other. B. The ability to do work.

B

According to the law of conservation of energy, a bouncy ball should never stop bouncing. However, we know that is eventually stops. Where does the energy go? A. Some gets converted into sound energy and escapes into the surroundings. B. Some gets converted into thermal energy and escapes into the surroundings. C. Both A and B

C

Sound Energy is A. The energy of a compound that changes as its atoms are rearranged to form new compounds. B. The total energy of the particles that make up an object. C. The energy caused by an object's vibrations. D. The energy of motion.

C

The law of _________________ of energy states that energy cannot be created or destroyed. A. Transformation B. Absorption C. Conservation D. Stability

C

Which of the following is the best example of increasing an object's potential energy? A. Rolling a bowling ball B. Turning on a light bulb C. Stretching a rubber band D. Dropping a pencil

C

As height increases, so does A. Thermal energy. B. Mechanical energy. C. Kinetic energy. D. Potential energy.

D

What device converts chemical energy to mechanical energy? A. Human B. Car C. Jet ski D. All of the above

D

Which of the following is a conversion from chemical energy to thermal energy? A. Coal is burned to boil water. B. Food is digested and used to regulate body temperature. C. Charcoal is burned in a barbeque pit. D. All of the above.

D. all of the above

Practice Problems: A 15kg textbook is sitting on a 1.20 m tall table. If the book is lifted 0.80 m above the table, how much gravitational potential energy does it have? With respect to the table? With respect to the floor?

Ep=mgh= (15)(9.8)(0.80) =120 J Ep=mgh= (15)(9.8)(2) = 294J

The Law of Conservation of Energy

energy cannot be created or destroyed; it can only change forms

Kinetic Energy

energy in the form of motion 1/2mass X velocity^2

Elastic Potential Energy

energy stored by objects that are stretched or compressed

Chemical Potential Energy

energy stored in chemical bonds

Gravitational Potential Energy

energy that are stored by objects above Earth's surface depends on 3 factors: 1.) acceleration due to gravity 2.) the greater the height, the greater the PE 3.) the greater the mass, the greater the PE

Calculating G.P.E

mass X 9.8 X height

Nuclear Fission

the splitting of an atomic nuclei

Mechanical Energy

the total amount of kinetic and potential energy in a system