A Level Physics notes ans questions: Equation of continiuty

The equation of continuity says that the rate of mass flow through a given tube at the entrance and at the exist is the same, if there is no other way for the fliud to get out from the pipe. Lets put things into a simpler form :

A1 x V1= A1 x V1

Lets prove this equation:

Mass flow rate = mass flowing through the pipe in one second
                               = V x D /t (t=1 second)
                               = l x a x D  /t
                               = A x D x V ( l/t)
 Because the mass flow rate is constant from th equation of continiuty
A1 x V1 x D =  A2 x V2 x D

Equation of continuity and Bornoulllis law A Level Physics Notes Questions Answers  and Explanation

 As Density D is the same on both sides ,it gets canceled out.

So :,
A1 x V1 = A2 x V2

You must be able  to prove this equation , and using this equation you will be able to solve many problems in your A Level Physics exam paper.

For a set of questions and Answers onthis section of A Level Physics Please click here.

A Level Physics:Dynamics and Motion(formula and solved problems)

Dynamics Physics a level Motion in a srtraight line. Speed is different from velocity .Speed is the distance moved in a unit time , while velocity is the distance moved in a unit time in a particular direction. We can assume that a car is moving in a stright line with a velocity of 5 m/s ,than it is evident that the car travels a distance of 5m in one second without any change in direction, The equation which is used is: velocity = distance moved /time taken (use this formula in exams and when doing problems) Example: A motor bike travels 1000 m in 6 minutes,find the speed of the motor bike? (dear students take note of the wording please the question asks for the speed of the bike as it doesnot say that the bike travelling in a specific direction. If you have any further doubts about the specifications about the differenciations of speed and velocity and the problems involved in them please be kind enough either to email me at veeradinesh85@gmail.com or just leave a comment below.Any type of doubts are welcome even ifthey are not from this section.

A Level Notes: Law of Floatation

The principle of floatation says that for a floating objects,the weight of the object equals the upthhrust exerted by a fluid on that object.
ie: When a body floats in a liqiud , it is in equilibrium and is acted upon by two forces only,its weigght and the upthrust.

These two forces must be equal and opposite to satisfy the conditions of floatations,

 Weight of object = upthrust

But as we already know from Archimedes principle that U=Vx Dx g N..............................1


So hence,  Weight=VDg..........................2

With these two equations you must be able to solve problems on the law of flatation,

I wish you all the best in your exam.If you need any other notes or information in this topic or any other area of physics email me or simply put a comment.

Weights and Mass A Level Physics

The weight of an object is defined as the force acting on it due to the gravitational force .The weight of a object can be measured by attaching it to a spring balance and reading the scale.

But mass is differen in the way that it is equal to the density of the object multiplied by the volume of the object.
Mass is universally constant meaning it doesnot change from one planet to the other just as weight changes.

(a level revision,notes,syllabus,problems solved,help,tutorial)

Hydrostatics.
This is the study of fliuds and their behaviors.

Circular motion Physics A Level

Circular Motion

What is exactly meant by circular motion ? It is the physical motion of an object moving in a circular path about a center. There are circular motion in many areas of our life, for example the hour and minute hand of a clock displays circular motion, and also the planets and moons in the solar system show circular motion.(Although planets move in elliptical paths we consider them to be moving in circular paths for calculation purposes.)

First lets look at some important maths that are a essential for understanding todays topic of circular motion.

180 degrees = π radians 360 degrees = 2π radians 90 degrees   = ½ π radians For very small angles :     sin θ  = θ radians                                                        tan θ=  θ radians

* Ѡ (the angular velocity) is the angle in radians through which the the object in circular motion has turned in one second.

*ἀ (the angular acceleration) is the increase in the value of Ѡ (the angular velocity) per second.

* r –denotes the radius of the circle that we are dealing with.

The types of circular motion:

1.      Horizontal circular motion

2.      Vertical circular motion

3.      Conic pendulum

Different situation or means of circular motion:

1.      Revolving at a constant speed around a circle.(eg: hands of a clock)

2.      Revolving with variable speeds (that is with constant angular acceleration or constant angular deceleration)

*(eg : A car starts from rest and its wheels show constant angular acceleration)

1.   Constant speed circular motion:

A particle P revolves at a constant speed in a circular path. At time ( t=0), P is at P₁. After a time t , P is there as shown in the diagram. Consider the radius of the circular path to be r.

S=r θ  (θ in radians)

Velocity

 V=s/t

V=r θ/t  (from equation 1)

θ/t= Ѡ (angular speed)

Ѡ= θ/t

(linear velocity)  V= r Ѡ ( angular velocity)

Definition of angular speed:

The rate of change in angle is the angular speed.

The unit of angular speed is rad/s.

The Dimension of angular speed is T^-1

Angular speed is a scalar quantity because it has only a magnitude.

Angular velocity id a vector quantity ,because it has both direction and magnitude.

Rotation with a constant speed:

If a body is rotating with a constant speed then tangential acceleration is equal to zero.But still there an acceleration on the body toward the center. THIS IS CALLED CENTRIPETAL  ACCELERATION!

Errors and their types:

Errors can be grouped into two groups :
1 systematic error


 systematic: e.g. constant error (in all readings)
    cannot be eliminated by averaging
    error in measuring instrument B1
 
2.random errors
random: e.g. readings scattered (equally) about true value
    error due to observer
    can be eliminated by averaging
        (only if averaging not included for systematic


It is very to know these by heart as you will be given a direct question about errors in your physics AS exam.

Projectile motion A level Physics

Projectile motion is a special case of two dimensional motion with constant acceleration. Here, force due to gravity moderates linear motion of an object thrown at certain angle to the vertical direction. The resulting acceleration is a constant, which is always directed in vertically downward direction.
                                                         read the rest at http://cnx.org/content/m13837/latest/
Problems on Projectile motion can either start from the botom with an object thrown at a angle witha speed.or it can startfrom a height like a cliff with the object either thrown upward or horrizontally with an initial speed.Which ever the problem is about the following formulas can be used to tackle the questions..

Remember these formulas for doing problems on projectile motion:



The maximum Height that the particle has travelled = u2sin2o(theta)
                                                                       2g
 The time taken for the particle to  reach the ground again   = 2u sino
                                                                                       g
Range     = u2sin2o
                  g

Todays question: about Deriving a SI unit

 Expresse  the volt in terms of SI base units?

Ok lets get started:
We know that P=VxI
                             Fx d=VxI
       F is  kgm/s2  d is in m  and I is in A
So V= kgm2s-2A-1

If you need anymore help in deriving the SI units of other quantities just leave a comment and I shall reply.

Lets do a physics question (a level)

Lets do a physics question (a level)

welcome back

The question is as follows

Q:A laser emits light of wavelength 600 nm
. What is the distance, expressed as a number of wavelengths, travelled by the light in one second?

 We know that

 1 nm=10^-9m
 therefore:                           600nm =6 x 10^-7m

 we also know that the speed of light is= 3 x 10 ⁸m/s
 so v= f x L

 note that the question asks for the frequency

so: f= 3 x 10⁸/6 x 10^-7 Hz
 the answer is f= 5 x 10¹⁴ Hz