1. Energy & Its Impact on Global Society
Jerome K. Williams, Ph.D.
Saint Leo University
Dept. Mathematics & Sciences

2. Chapter 2: Energy Mechanics
Critical Thinking in Science
Forms of Energy
Primary Energy Souces & Energy Conversions
Motion

3. Critical Thinking in Science
Scientists seek to understand the physical world and how it works
Making Observations
Formulating Hypothesis
Testing Hypothesis by Experimentation

4. Critical Thinking in Science
A tentative statement that tries to generalize a series of observations is a hypothesis.
A hypothesis that has been supported by a large number of observations and experiments is called a theory.

5. Forms of Energy Mechanical Energy Two Kinds
Kinetic Energy (KE) – energy of motion
Potential Energy (PE) –energy of position

6. Forms of Energy

7. Forms of Energy Chemical Energy – use fossil fuels & food for energy
Nuclear Energy- energy found in atomic nucleus
Thermal Energy: transfer heat between objects
Electrical Energy – energy produced at power plants or stored in batteries
Light (Radiant) Energy – also called electromagnetic radiation (ER); this covers a wide range of sources from radio and TV waves to X-rays and solar energy

8. Primary Energy Sources & Energy Conversions
Chemical
Nuclear
Radiant
Energy Conversion Processes are how primary energy sources are converted to an end use (powering a car, heating a home, using a laptop computer, etc.)

9. Primary Energy Sources & Energy Conversions

10. Motion Speed = distance traveled per unit time
Velocity = similar to speed except it must include direction of travel
Acceleration = change in velocity per unit time

11. Motion

12. Motion
Force = push or pull on an object by other objects in environment
Newton’s 2nd Law of Motion = acceleration of an object is directly proportional to the net force acting on it and inversely proportional to the object’s mass

13. Motion Units for Speed: Units for Force:
Examples m/s, km/h, ft/s, mph
Units for Force:
Examples Newton (N), Pound (lb)
Conversion Factors: 1 lb = 4.45 N
Table 2.4

14. Example Problem 2.1
A 2000 kg car is acted on by a force of 6000 N by its wheels. Also acting on the car is a force of friction of 800 N. What is the car’s acceleration?
Answer: 2.6 m/s2

15. Example Problem 2.2
Brakes are applied to a 1900 kg car moving at 80 km/h. In a time of 4.0 seconds, its velocity decreases uniformly to 30 km/h. What is the net force acting on the car?
Answer: N