Physics Chapter 1

Physics is the understanding of how and why something happens. All sciences, Engineers, Architects, Healthcare professional, Computer Programmers, Video game designers and even machinist need physics to understand their world and careers.

For this semester the topic that will be covered are:

  • Kinematics [ 1 and 2 D, Linear, and rotational motions]
  • Forces
  • Mechanical Energy
  • Basic Fluid Mechanics
  • Basic Thermal Physics and Thermodynamics

Chapter 1 covers the units and conversions that are important for the class. We will be using SI units on the tests. However, homework will have other units. Important units to understand are:

  • Length – meters (m)
  • Mass – kilograms (kg)
  • Time- Seconds (s)
  • Temperature – Kelvin (K)

Rules for units

When multiplying / dividing, you can have different units but the product will correspond with the action taken. [10m / 5s = 2 m/s ].

When you are adding / subtraction quantities they have to have the same unit.

Why are these rules important to physics? Well it has to make physical sense in the equation for the result to make sense. If you put together an equation and you don’t follow the rules, then you have made a mistake and the result will be wrong.

We can combine these base units through multiplication and division to make compound units like:

  • Force – Newton (N) : kg m/s^2
  • Pressure – Pascal (Pa) : N/m^2
  • Velocity – [length/time] : m/s
  • Acceleration – [lenth/time^2]: m/s^2

Physics, as well as other sciences, use significant digits in order to account for accuracy and dismiss uncertainty of numbers. When you take a measurement, the smallest number you can see with accuracy is the smallest significant digit. Some times in the arithmetic there will be numbers generated smaller than this number. They are considered non significant.

Rules to Significant Digits

  • Any number that is not a zero is significant
  • Zeros at the end and after the decimal are significant
  • Zeros in between non-zeros are also significant
  • Zeros in between significant digits are significant

Math involving Significant Digits you want you answer to be the most accurate so you will take the least amount of significant digits.

In the metric system and SI units, it is important to remember the prefix meanings. This will help with scientific notation and help make the arithmetic easy to follow.

In this semester we will be using Coordinate systems and how they apply with trigonometry. The system we will be focusing on will be the Cartesian method in which x and y coordinates will be shown as (x, y). In this class you will need to understand the trig functions sine, cosine and tangent. For a recap, I linked a video below.

You should also remember the Trig Values at special angles and how to use them.

Using the definitions of sin and cos we can find any value for triangles which will be a basic skill needed for physics. We can also use Pythagorean Theorem in conjunction with trig functions in some cases. However, trig functions will be the easiest route.

Lets do an example:

Find the height of a building. A women in stand 20 m away for a building and from the ground (with a protractor) she can tell that the top edge of the wall is 60 degrees elevation. How tall is the building?

To find h, you can use tan function. Tan (60) = Opp/adj >> Tan 60 = h / 20 m

We can rewrite this to h = (20 m) tan (60). Which equals 35 m.

Lastly, we have two types of quantities that we will use. Scalars which are magnitudes such as mass, speed, time and energy. As well as, vectors which have both magnitude and direction. Vectors include velocity, acceleration and force.

Vectors can be broken down into components of x and y using trig functions.

You can add vectors, however, they must be in like components of the x and y. For example, Vector A has components A(x) = 2 and A(y) = 4. Vector B has components B(x) = 5 and B(y) = 6. If we wanted to add them together to make Vector C we need to have sure the x and y components are added together by component. So Vector see C(x) = 2 + 5 = 7 and C(y) = 4 + 6 =10

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