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Chapter 1

Quantities and Units
Uncertainty
Scalers and Vectors

Chapter 2

Kinematics
Motion

Chapter 3

Work - Power - Motion

 

Chapter 4

Force And Collisions

 

Chapter 6

Electricity

 

Chapter 1

Quantities and units!

 

A PHYSICAL QUANTITY is a feature of something which can be measured.
I.E. LENGTH WEIGHT OR TIME OF FALL

 LARGE   and   SMALL quantities are usually expressed in scientific notation
image 2        image 4         image 6
The elephant is large in comparison with the boy but small in comparison with the sky scraper.
                                        

The SI SYSTEM of UNITS!
image8     

  1. All quantities have a magnitude and a unit.
  2. The SI base units of mass, length, time electric current, thermodynamic temperature, and amount of substance are the Kilogram, metre, second, ampere, Kelvin and mole respectively.
  3. Units if all mechanical, electrical and thermal quantities may be derived in terms of these base units.
  4. Physical equations must be homogeneous. Each term in an equation must have the same base units.

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Uncertainty

Uncertainty…

           There are TWO different types of uncertainty, Systematic and Random. They can each be defined as the following:

Systematic uncertainty (or ‘error’) will result in all readings being too large or too small. This Uncertainty cannot be eliminated by taking an average of several values.
Examples include:

  1. Non- zero reading on a meter
  2. Incorrectly calibrated scale
  3. Reaction time of experimenter

Random Uncertainty gives a rise to the scatter if readings about the true value. The uncertainty can be reduced by repeating readings and taking and average.
Examples include:

  1.  Reading a scale
  2. Measuring out a certain volume of liquid
  3. Miss-reading a scale from the wrong position.

WOAH!

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Scalars and Vectors

 

A scalar quantity can simply be defined as a quantity that has magnitude,
As for a Vector, that is a Quantity that has both Magnitude and DIRECTION

 

EXAMPLES

  • Mass: Scalar
  • Speed: Scalar
  • Weight: Vector
  • Force: Vector

 

A VECTOR QUANTITY MAY BE REPRESENTED BY AN ARROW, WITH THE LENGTH OF THE ARROW DRAWN TO A SCALE TO THE GIVEN MAGNITUDE.

  • Horizontal Component of a vector; FcosANGL

Vertical Component of a vector; FsinANGL

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Chapter 2

Kinematics

Ave. Speed= distance covered
                     Time Taken

Speed and Velocity are generally perceived to be the same thing, however in physics that are completely different.
The Difference between speed and velocity, is that a velocity is used to represent a vector quantity: the magnitude of how fast the particle is moving, and the direction at which it’s moving. Speed does not have a associated direction. Making them differ.

Ave. Velocity= displacement
                        Time Taken
FOUR EQUATIONS OF UNIFORM MOTION

  • v= u + at
  • s=ut +1/2 at^2
  • v^2= u^2+2as
  • Ave. V = (u+v)/2

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image2        MOTION!

FREE FALL ACCELERATION:
All objects fall with the same uniform motion(g), its value is 9.8 m/s^2 and is directed downwards.
Eventually objects in free fall reach terminal velocity which is a maximum velocity.

PROJECTILE MOTION
Galileo first gave an accurate summary of this particular type of motion. He did so by splitting the motion in to its horizontal and vertical components.
Fx    & Fy            Each representing the vertical and horizontal components respectively.

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Chapter 3

Work Power Motion

ii WORK, POWER, & MOTION!!

  • WORK; “I am going to work today”… WRONG
  • WORK;  “ I have finished my homework”…WRONG
  • WORK; “Work is done when a force moves the point at which its at” … RIGHT

 

When a force of one Newton moves its point of application by one meter in the direction of the force, one joule of work is done

WORK DONE= pressure X change in volume.

THE ABILITY TO DO WORK IS CALLED ENERGY

  • POTENTIAL ENERGY: MGH

Where m= mass , G= Gravitational pull, H= Height of object.

  • KINETIC ENERGY: 1/2MV^2

Where Mass times velocity squared is divided my 2.

HOOKE’S LAW
Provided the elastic limit is not exceeded, the extension of a body is proportional to the applied load.

F= K times the change in L.
K is the elastic constant.

 

ENERGY CAN NOT BE CREATED OR DESTROYED ONLY TRANSFERRED FROM ONE FORM TO ANOTHER….

Power is the rate of doing work.

Work done= power X time taken

Power= WORK DONE 
               TIME TAKEN

Power, like energy is a scalar quantity

Power= force X speed

 

TORQUE
The turning effect of a force is called torque

The torque is a force defined as the product of the force and the perpendicular distance of the line of action of the force from the pivot.

COUPLE
A couple consists of two forces equal in magnitude but opposite in direction

 

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Chapter 4

Force and Collisions

Newton’s Laws

  1. Every body continues in it’s state of rest, or of uniform motion in a strait line, unless compelled to change that state by a net force
  2. For a body of constant mass, its acceleration is directly proportional to the net force applied to it.
  3. Whenever a body exerts a force on another, the second exerts an equal and opposite force on the first.

 

Force= mass x acceleration (F=ma)

*The property of a body to stay in a state of rest or uniform motion is called inertia*

Weight=mass x the acceleration of free fall

Momentum = mass x velocity
P = mv

*the force acting on a body is equal to the rate of change of its momentum*

F =ma

*if no external force acts on a system, the total momentum of the system remains constant, or is conserved*

*if a constant force acts on a body for a time, the impulse of the force is given by the force x change in time*

COLLISIONS

Two kinds:

  1. If the collision is elastic the kinetic energy before collision is equal to the kinetic energy after
  2. Collisions in which total kinetic energy is not the same before and after the event are called inelastic

 

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Chapter 6

Electricity

Charge = current x time

*the coulomb is that charge passing a point in a circuit when there is a current of one ampere for one second*

*the Resistance(R) of a wire is defined as the ratio of the potential difference across the wire to the current in it*

R= V/I or Potential Difference/ Current

Potential Difference = energy transferred (or work done)/charge

V= W/q

Energy Transferred = potential difference x charge

W= Vq

Potential Difference = power/ current

V= P/I

Electrical Heating

Electrical power= Current squared x resistance

Electrical Power P= VI= I^2R= V^2/R

OHM’S LAW
For a conductor at constant temperature, the current in the conductor is proportional to the potential difference across it.

*The resistively of a material is numerically equal to the resistance between opposite faces of a cube of the material, of unit length and unit cross-sectioned area*

Kirchoff’s Laws

  1. the sum of the currents entering a junction in a circuit is always equal to the sum of the currents leaving it.
  2. The sum of the electromotive forces in a closed circuit is equal to the sum of the potential differences.

*the terminal potential difference is the p.d. between the terminal of a cell when a current is being delivered*

*A supply delivers maximum power to a load when the load resistance is equal to the internal resistance of the supply*

 

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