Introduction to Physics Physics is the science that seeks to understand the fundamental principles underlying the behavior of matter, energy, space, and time. It encompasses a wide range of phenomena, from the interactions of subatomic particles to the movements of galaxies. The goal of physics is to develop theories and models that can explain and predict the behavior of the physical world. Historical Development of Physics The roots of physics can be traced back to ancient civilizations, where philosophers and scholars pondered the nature of the universe. However, it was the Greeks who laid the foundation for modern physics, with thinkers like Aristotle and Archimedes making significant contributions to our understanding of motion and mechanics. The Scientific Revolution of the 16th and 17th centuries marked a turning point in the history of physics. Figures like Galileo Galilei, Johannes Kepler, and Isaac Newton revolutionized our understanding of motion, gravity, and the laws governing the physical world. Newton's laws of motion and universal gravitation, in particular, laid the groundwork for classical physics. Classical Physics Classical physics, also known as Newtonian physics, describes the behavior of macroscopic objects moving at everyday speeds. It encompasses Newton's laws of motion, which describe the relationship between an object's motion and the forces acting upon it. These laws form the basis for understanding the motion of objects on Earth and in space. Classical physics also includes the study of thermodynamics, which deals with the relationships between heat, energy, and work. The laws of thermodynamics govern the behavior of systems ranging from steam engines to the entire universe. Modern Physics The 20th century saw the development of modern physics, which revolutionized our understanding of the universe on both the largest and smallest scales. Two major developments in modern physics were the theory of relativity and quantum mechanics. Quantum Mechanics Quantum mechanics is the branch of physics that describes the behavior of particles on the smallest scales, such as atoms and subatomic particles. It is based on the principle of wave-particle duality, which states that particles exhibit both wave-like and particle-like properties. Quantum mechanics has led to groundbreaking discoveries in areas such as solid-state physics, quantum optics, and quantum computing. Relativity Relativity, developed by Albert Einstein, revolutionized our understanding of space and time. It consists of two major theories: special relativity and general relativity. Special relativity describes the behavior of objects moving at high speeds, showing that time and space are intertwined in a four-dimensional continuum known as spacetime. General relativity extends this to include gravity, describing it as the curvature of spacetime caused by the presence of mass and energy. Particle Physics Particle physics is the branch of physics that studie

1. PHYSICS 231
INTRODUCTORY PHYSICS I
www.pa.msu.edu/courses/phy231
Scott Pratt
prattsc@msu.edu
(517) 355-9200, ext. 2016
Office Hours:
Monday, 9-10:30 AM in 1248 BPS

2. Course Information
http://www.pa.msu.edu/courses/phy231

3. Succeeding in Physics 231
1) Do your homework (yourself)!
2) Use the help room (1248 BPS) !
3) Make sure you understand both “why” and “why
not”
4) Interrupt the lecturer!

4. General Physics
• First Semester (Phy 231)
• Mechanics
• Thermodynamics
• Simple harmonic motion
• Waves
Second Semester (Phy 232)
• Electromagnetism
• Relativity
• Modern Physics
• (Quantum Mechanics, …, etc.)

5. Mechanics
• Half the course
• Quantified largely by Galileo
• Problems involve:
velocity, acceleration, mass, momentum, energy,
torque, angular momentum, moment of inertia…

6. UNITS (Systéme Internationale)
Dimension SI (mks) Unit Definition
Length meters (m) Distance traveled by light in
1/(299,792,458) s
Mass kilogram (kg) Mass of a specific platinum-
iridium allow cylinder kept by
Intl. Bureau of Weights and
Measures at Sèvres, France
Time seconds (s) 9,192,631,700 oscillations of
cesium atom

7. Standard Kilogram
at Sèvres

8. Dimensional Analysis
Dimensions & units can be treated algebraically.
Variable from Eq. x m t v=(xf-xi)/t a=(vf-vi)/t
dimension L M T L/T L/T2

9. Dimensional Analysis
Checking equations with dimensional analysis:
L
(L/T)T=L
(L/T2)T2=L
• Each term must have same dimension
• Two variables can not be added if dimensions
are different
• Multiplying variables is always fine
• Numbers (e.g. 1/2 or p) are dimensionless

10. Example 1.1
Check the equation for dimensional consistency:
2
2
2
)
/
(
1
mc
c
v
mc
mgh 


Here, m is a mass, g is an acceleration,
c is a velocity, h is a length

11. Example 1.2
L3/(MT2)
Consider the equation:
Where m and M are masses, r is a radius and
v is a velocity.
What are the dimensions of G ?

12. Example 1.3
Given “x” has dimensions of distance, “u” has
dimensions of velocity, “m” has dimensions of
mass and “g” has dimensions of acceleration.
Is this equation dimensionally valid?
Yes
Is this equation dimensionally valid?
No

13. Units vs. Dimensions
• Dimensions: L, T, M, L/T …
• Units: m, mm, cm, kg, g, mg, s, hr, years …
• When equation is all algebra: check dimensions
• When numbers are inserted: check units
• Units obey same rules as dimensions:
Never add terms with different units
• Angles are dimensionless but have units
(degrees or radians)
• In physics sin(Y) or cos(Y) never occur unless Y
is dimensionless

14. Example 1.3
Grandma traveled 27 minutes at 44 m/s.
How many miles did Grandma travel?
44.3 miles

15. Prefixes
In addition to mks units,
standard prefixes can be used,
e.g., cm, mm, mm, nm

16. Example 1.4a
The above expression yields:
a) 40.11 m
b) 4011 cm
c) A or B
d) Impossible to evaluate (dimensionally invalid)

17. Example 1.4b
The above expression yields:
a) 4.5 m kg
b) 4.5 g km
c) A or B
d) Impossible to evaluate (dimensionally invalid)

18. Example 1.4b
The above expression yields:
a) -1.5 m
b) -1.5 kg m2
c) -1.5 kg
d) Impossible to evaluate (dimensionally invalid)