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.

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Pie de foto: : 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

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Pie de foto: : 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 MassDone using an Analog or Digital Scale.Measuring Volume of a LiquidDone 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.

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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+BThere 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.

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Pie de foto: : 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.

Components (binary/octet-stream)

Pie de foto: : 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

Acceleration Formula (binary/octet-stream)

Pie de foto: : 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.

Ticker Tape Timer (binary/octet-stream)

Pie de foto: : 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.

Displacement Graph (binary/octet-stream)

Pie de foto: : 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.

Velocity Time Graph (binary/octet-stream)

Pie de foto: : 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'.

Simple Pendulum (binary/octet-stream)

Pie de foto: : 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.