Physics

Physical Quantities

• Base Quantities:
• A quantity that can be measured, example length, mass, weight, time etc.
• A quantity must contain a numerical value and unit, example mass of object equals 60 kg but weight is equal to 600 N.
• When units are not present it is incorrect
• Dimension less quantities are the exception to this rule, example refractive index and relative density.
• Physical quantities can be separated into base quantities and derived quantities.
• 
• Bildunterschrift: Table of Base Quantities and S.I. Units

Physical Quantities

• Derived Quantities:
• A combination of base quantities.
• A derived unit is expressed as products or quotients of base units
• Example, Speed =Distance/Time =Meter/ second =m/s
• 
• Bildunterschrift: Derived Quantities and there S.I. Units

Decimal Places

• Number of places after the decimal point, example, 2.54 is written to 2 decimal points

Significant Figures

• Tells us about precision.
• Zeros at the front of a significant figure are not included.
• The ones in the middle are included.
• Example 5674 is written to 4 significant figures, 0.6423 as well.
• 6472 is written as 6470 to 3 significant figures, 6500 to 2 significant figures, and 6000 to one.
• Round up/ down to the nearest none zero number.

Standard Form

• A simple form of very large or small quantities.
• Example: 330 in standard form is 3.3 x 10^2 or 0.022 is 2.2 x 10 ^(-2)

Types of Errors

• Random Errors:
• Caused by unknown, unpredictable events that may occur during the experiment.
• Changes may occur in measuring instruments and environmental conditions, example, a wind surge.
• Systematic Errors:
• Occurs when something is wrong with the measuring instrument or its data carrying system
• Or if wrong readings are taken off of the instrument.
• Parallax Error:
• Mostly committed error in physics.
• Occurs when readings aren't taken at eye level.

Instruments and what they measure

• Measuring Mass
• Done using an Analog or Digital Scale.
• Measuring Volume of a Liquid
• Done using a measuring cylinder, it is read at eye- level, to avoid errors.
• Measuring Volume of a Solid
• If the object is regularly shaped like a rectangle, it would be L x B x H
• If the object is irregularly shaped we use 2 things.
• Displacement Can
• Measuring Cylinder

Simple Pendelum

• A simple pendulum hanging from a string of length, l.
• A fixed pivot point, p.
• When displaced to initial angle the pendulum will swing back and forth with periodic motion.
• Factors Affecting a Simple pendulum
• The size of the swing ( amplitude).
• The size of the bob.
• The size/ length of the thread.
• \Note well:
• The swing is one complete cycle
• The time for a complete cycle, called the period of cycle.
• 

Plotting a Graph

• A straight line is in the form y = mx + c.
• x = x- axis coordinates
• y = y- axis coordinates
• m= Gradient
• c= y - intercept (constant)

Scalar and Vector Quantities

• Scalar:Has Magnitude only
• Mass
• Time
• Temperature
• Energy
• Power
• Speed
• Work
• Resistance
• Vector:Has Magnitude and Direction
• Velocity
• Acceleration
• Friction
• Weight
• Momentum
• Force

Vectors (to be continued)

• Vectors can be represented by a line drawn in a particular direction.
• The length of the line is the vector's magnitude.
• The direction of the line is the direction of the vector.
• Two forces acting in the same direction, the net/ total cost can be shown as follows:
• 4N ---------> + 6N -----------------> + 10 N -------------------------------->
• Two forces acting in opposite directions, the net/ total force can be shown as follows:
• 6N -----------------> + <------------ 4N = 2N ------>

Vectors (cont'd)

• Two vectors are equal if the have the same magnitude and direction.
• The addition of 2 vectors A&B yields another vector, the resultant force of their sum.
• It is written as A+B
• There are 2 methods to adding vectors:
• Triangle of Vectors
• Parallelogram of Vectors
• The resultant force of 2 vectors can be drawn in the shape of a triangle of vectors.
• A&B are drawn so that the tail of Vector A touches the head of Vector B. The resultant will be an arrow from the tail of A to the head of B.
• 
• Bildunterschrift: Triangle of Vectors

Vectors cont'd - Components

• This is the sum of 2 vectors.
• They are called components of the original vectors.
• They are taken at right angles to each other.
• The component 'F' can be found by Scale Drawings or by calculation.
• To Calculate 'F' using the y-axis, use Fsinθ.
• To Calculate 'F' using the x-axis, use Fcosθ.
• 
• Bildunterschrift: Components

Motion

• Speed - Calculated using the formula Average speed = Distance/ Time
• Velocity - Calculated using the formula, Velocity = Displacement/ Time
• Acceleration - Calculated using the formula, Acceleration = Change in velocity/ Time
• Acceleration - Calculated using the formula, Acceleration = Final Velocity - Initial Velocity/ Time
• 
• Bildunterschrift: Formula for Acceleration

Motion cont'd - Ticker Tape Timer

• Can be used to determine velocity and acceleration.
• When the tape is pulled, 50 dots per second are produced.
• Evenly spaced dots show uniform velocity.
• If the distance between dot intervals increase.
• Increasing distance between dots shows acceleration.
• Decrease in distance between dots show deceleration.
• 
• Bildunterschrift: Ticker Tape Timer

Displacement vs Time Graph

• This is a graph obtained when the displacement of an object in motion is plotted against time.
• If the graph is a straight line then velocity is uniform or constant.
• 
• Bildunterschrift: Displacement vs Time Graph showing Uniform Velocity

Velocity vs Time Graph

• This is a graph obtained when Velocity is plotted against Time.
• The gradient of the line is the magnitude of acceleration.
• A straight line indicates constant acceleration.
• The area below the graph gives the displacement, or distance travelled.
• 
• Bildunterschrift: Velocity vs Time Graphs

Acceleration Due to Gravity

• This is given the symbol 'g'.
• It is equal to 10 m/s.
• This is equivalent to 10 N/kg.
• It can be determined by using a simple pendulum experiment.
• The value of acceleration due to gravity is found using the equation g= 2h / t^2.
• g - gravity
• h - height
• t - time taken for the ball to fall through the height 'h'.
• 
• Bildunterschrift: Simple Pendulum Experiment

Forces

• A force is a push or pull.
• When applied, it can cause an object at rest to move, an object in motion to change speed or direction and change in shape of an object.
• There are several kinds of Forces, gravitational forces, electric forces, magnetic forces, nuclear forces etc.
• The symbol of force is 'F', and its unit is the Newton, N.
• Forces is a vector quantity, represented by its size, direction and point at which the force is applied.