What is Physics??. The science of matter and energy and of interactions between the two. Physics is concerned with the description of nature – the description and explanation of natural phenomena in our physical world.
Matter, Energy, Space, and Time
There are different Systems or Conventions to flesh out these units of measure
The most commonly used one in Science is the Systeme Internationale (SI)
It is also known as the mks system
1 kilogram weighs
1 meter is
3.3 feet long
1 second is 1 second in any unit system
Kilo (k) means multiply by 1000
1 kilogram (kg) = 103 = 1000 grams (g)
Centi (c) means divide by 100
1 centimeter (cm) = 10-2 = 0.01 meter (m)
Milli (m) means divide by 1000
1 millimeter (mm) = 10–3 = 0.001 meter (m)
Other prefixes may be found on page 3 in your book.
Units behave like algebraic quantities.
When identical units are divided, they
Convert 65 miles/hour to kilometers/hour:
Angel Falls in Venezuela has a total drop of 979 m.
Convert to feet:
How many seconds are there in one day? Find out by converting 1 day into seconds, by canceling units.
For right triangles only!
H2 = A2 + O2
The peak of Mt. Fuji in Japan is ~12,400 ft high. A person, several miles away, notes that the angle between the level ground and the peak is 30o. Find the distance (in feet) from the person to the point on the level ground directly beneath the peak.
Scalars are numbers
Examples: 10 meters
Vectors are numbers with a direction
Example: 10 meters to the right
75 kilometers/hour north
Scalar: 25 meters
Vector: 25 meters north
Scalar: 25 meters
Vector: 25 meters east
To add two vectors, A + B
1. place the head of one vector
on the tail of the other vector
2. draw a new vector from
the tail of the first to
the head of the second
3. This new vector is
is called theresultant
A+ B= C
To subtract two vectors, A-B
1. Multiply vector B by -1: A + (-B)
2. Then simply add A and -B,
3. A + -B = C
A = x + y
We call x and y the
components of the vector A.
A+ B = C
Add the x components of A and B to each other to get the x component of C.
Then, add the y components ofAand B to each other to get the y component of C.
You travel 2 km due East on 26th street, then turn right on Main street and head Southeast for 1 km, what are the components of your displacement?
If B has a magnitude of 25 kilometers in a direction 30 degrees North of East, what is the x component of B?
If A has a magnitude of 10 meters, and is pointing 45 degrees South of East, what is the magnitude (length) of the vector Ay?