Make sure you understand how to do the homework problems. They illustrate the principles with practical examples. A few are guaranteed to be on the exam.

IMPORTANT CONCEPTS

Chapter 1. Overview

This chapter summarizes the present status and consequences of

(1) our increasing level of technology
(2) increasing population (exponential increase)
(3) increasing standard of living
(4) limitations of resources (here: energy)
(5) limitation to the load that the environment can bear (pollution, degradation)
(6) possible long term effects such as climate change due to human influences.

Two important points:
(1) we are already at or close to a turning point in our supply of one of the most versatile, inexpensive, easily handled and essentially nonrenewable fuels, oil.
(2) we are approaching the maximum human population that this world can "reasonably" support, that is, without too much of a degradation of our current life styles.

However, no one can foresee the future and things may be very different than we can imagine!

NO NEED TO MEMORIZE FACTS. The emphasis is on common sense and reasoning, and most of this material is recognized by educated people who are reasonably aware of their surroundings.
 

Chapter 2: Energy mechanics.

• Different forms of energy: potential and kinetic, transformation of various forms of potential energy (gravitiational, kinetic, chemical potential) to other forms.

• Mechanical energy, which is easily defined and measured, serves as the definition of all other forms of energy. Energy is measured in Joules but in the US, calories and Btu are also used.

• Review definitions of speed, velocity (speed with direction), acceleration, distance, time.

• UNITS: kg, meters, seconds (Joules). Cal and Btu are relative measures.

We define

• KE = energy of motion = 1/2mv²

• gravitational (PE = mgh) where g = 9.8 m/s²
• PE of compressed spring is second example.

A force (F) causes a mass (m) to accelerate (change its velocity by acceleration a)

the rule is
                a = F/m.  (Newton's Second Law)   Force is measured in Newtons.

Mass is not weight, it is "inertia" or resistance to acceleration. Mass is measured in kg (which is also used as a weight in most cultures). The earth also exerts a force due to gravity on a mass. Weight (measured in Newtons) is mg. Newton's second law works on the moon or in outer space.

We can define

                WORK = force x distance (Fd) = change in energy (PE or KE).
 

Notes: More than one force can operate at a time.
If a mass is accelerating, there is a net force acting on it. If it is not accelerating, the NET force is ZERO.

                Power = rate of doing work = Joules / second = watts.

Chapter 3.

Conservation of energy: Energy is never created or destroyed, merely converted into one form or another. Often, it is converted into heat which is less useful than other forms of energy.

The most commonly observed form of conversion is PE into KE and vice versa. A car rolling up a hill converts KE into PE which can then be converted back into KE when the car rolls back down.

Hydroelectric power converts gravitational potential energy of falling water into kinetic energy, then to electrical energy by rotating turbines.

We convert chemical energy of food (potential energy) into heat and mechanical energy (like when riding a bike).

Heat is stored as internal energy, which is often a form a KE (kinetic energy of molecules). Friction can convert an object's energy (say, kinetic energy of motion) into molecular KE as the object slows down.

            Efficiency = 100% x (useful energy or work output) / (energy input).

Most processes that convert natural energy sources (petroleum) into other useful forms of energy (electrical) are less than about 50% efficient. However, no energy is lost, it is just converted to heat! (Conservation of energy).

Chapter 4.

Heat and Internal Energy.

Heat is the transfer of energy from one object to another. An object cannot "contain" heat, rather it contains "internal energy". For many materials (for example, a gas in a container), internal energy is just the kinetic energy of the molecules. When we heat an object, the average KE of its molecules increases.

Temperature.
 

• Absolute temperature is a measure of the average amount of internal energy in an object.
• Three temperature scales: Celsius, Fahrenheit and Kelvin. Kelvin is absolute = Celsius + 273.
• At absolute zero (0 K) essentially all motion ceases.

Materials differ in their ability to store internal energy. We define this ability as their "heat capacity" or "specific heat", usually measured by weight.

                Heat added (Q) = mc (delta T)

Q = Joules, m = mass (kg), c = "heat capacity" or "specific heat", delta T = temperature change.

Originally calories (cal), Btu were units of heat as energy but these should be converted into Joules.
1 cal = 4.2 J
1 Btu = 1055 J.

Note: In units of cal/g/C or Btu/lb/F, the specific heat or heat capacity of water is 1 as this was the definition.

Water is a very unusual material! It stores a great deal of heat as internal energy (has a very large heat capacity), far more than most materials. This fact is responsible for the moderate climate of most islands and many coastal areas (depending on prevailing winds). In class, we did a "laboratory experiment" to show that different metals had different heat capacities, but all of them were less than that of water (usually by a factor of 5 to 10 or even more).

EXAM 1 through page 101.