.

Sunday, 5 August 2018

//// Leave a Comment

Machines: Mechanical Advantage, Velocity Ratio and efficiency formula

Mechanical Advantage, Velocity Ratio, efficiency

Machines

A machine is a device that makes work to be done easier and faster. It uses a basic concept of applying effort to overcome load.

Read More

Sunday, 29 July 2018

//// Leave a Comment

Liquid expansion: Real and apparent expansion, cubic expansivity.




Expansion of liquid; Real and apparent expansivity

Like solid, liquid expands on heating and contracts on cooling, because liquid is always held in a container, the expansion of liquid is always complicated because of the expansion of the container itself.

Read More

Monday, 23 July 2018

//// Leave a Comment

Physics: Anomalous Expansion of Water


Anomalous expansion of water

Anomalous expansion of water

This means something that is unusual. The temperature range of water from 0°C to 4°C is unlike most substance because is volume decreases as the temperature increases. 

Read More

Friday, 6 July 2018

//// Leave a Comment

Principles of Expansion: Advantages,Bimetallic strip, Uses in Electric iron, Fire alarm and thermostat


All about Expansion


Expansion of objects 

The expansion of an object is the process of increasing in size, amount or number. It is relative, when we tall about expansivity

Read More

Sunday, 30 July 2017

//// Leave a Comment

Physics: static electricity, electric charges and law of charges.

What is electricity?

     The is a form of energy that occurs when electrons flows through a conductor.


Areas Covered

  • Definition of static electricity
  • Nature of atoms of static electricity
  • Electricity charges
  • Law of charges
  • Conductor and insulator

Definition of static electricity


     Static electricity is  produced by the friction between two materials. For example, when rod is rubbed with silk.

Read More

Sunday, 26 March 2017

//// Leave a Comment

Physics: Introduction to radioactivity,types and properties.

radioactivity

Radioactivity

It is a spontaneous emission of radiation from a substance usually an unstable   .This process is also known as nuclear or radioactive decay). In the year 1896, Henri Becquerel a French scientist working with phosphorescent materials discovered that a uranium compound placed on a photographic plate which was covered with light black paper causing the plate to be exposed by blackening the pate itself. This implied that some sort of radiation was coming from the uranium which could pass through. The material was radioactive given-off radiation. Other scientists that researched on radioactivity were;v This radioactivity was spontaneous with the radiation being omitted without anything causing it apparently.

Types of radioactivity

From several experiments that have been carried out, it has shown that there are three different types of radioactive emission called;
 Alpha particles ; whose emission is easily stopped by paper or thick card
 Beta particles ; whose emission is easily stopped by aluminium sheet of different thickness and are negatively charged.
Gamma particles ; whose emission is easily stopped by thick sheet of lead.

types of radioactivity


Properties of alpha particles


      1)  Alpha rays are deflected by magnetic field.  
      2)      The direction of deflection of alpha rays shows that they are positively charged
      3)      They are relatively massive and so have more momentum and tend to continue in their direction of travel.
      4)      Alpha particles are absorbed by paper and air and are easily stopped aluminium thin sheet.
      5)      They have little penetrating power, travelling no more than 5cm. Being large, it is soon stopped by air molecules.
      6)      They are capable of stripping electrons from their atoms because alpha particles have comparatively large mass and momentum.


Properties of beta particles

     1)      There are also deflected by magnetic field but in the opposite direction to alpha particles.
     2)      The direction of deflection of beta rays shows that they are negatively charged with –e .
     3)      They are relatively light and as a result easily deflected.
     4)      They are deflected by different amount showing that they have varying speed..
     5)      They have good penetrating power of about 1 metre.
     6)      They can penetrate a few millimetre of aluminium.
     7)      They produce less ionisation in air than alpha particles.

Properties of gamma rays

    1)      They are electromagnetic waves similar to light wave but of very short wavelength.
    2)      They are electrically uncharged since they are not deflected by a magnetic field.
    3)      They are highly penetrative compared to the other two types and can only be stopped by thick lead blocks.
   4)      They have high penetrating power compared to the other two types.
   5)      They have much less ionisation than alpha rays.
Read More

Sunday, 12 March 2017

//// 9 comments

Physics: Thermal, linear, area and cubic expansivity

Thermal expansivity


Expansivity

 This is defined as amount a material expands or contracts per unit length, per-degree change in temperature.
The addition of heat will usually cause expansion of the body. during expansion, the dimension of the body increases.

Read More

Friday, 7 October 2016

//// Leave a Comment

Physics: Equations of Motion, derivation, Questions and solutions


EQUATIONS OF MOTION

In my last article, The definition and types of Motion were discussed. Now this is an article to better understand Equations of motion with several questions solved. 

Related Terms

  • Displacement: It is the distance moved in a specified direction. It is a vector quantity.
  • Distance: It is the magnitude of separation between two points. It is a scalar quantity.
  • Speed: It is the rate of change of distance with time. It is a scalar quantity.
  • Velocity: It is the rate of change of displacement with time. It is a vector quantity.
  • Acceleration: It is the increasing rate of change of velocity with time. It is a vector quantity.
  • Retardation: It is the decreasing rate of change of velocity with time.

                    Equations of motion


1) 

2)

3) 

4) 


Derivation

Average speed = s/t

              (V+u)/2 =s/t

where, V =final velocity
              U = Initial velocity
              S = Distance
              T = time
Make "s" subject of the formula.

      ..........(1)

Average acceleration= change in Velocity/time

        a = (v-u)/t    
             
        at = (v-u)

        V = U + at ...........(2)

Substitute (2) in (1)
               
        S =[ (u + at +u)/2]t.

        S =[(2u+at)/2]t
           
        ........(3)
From (2)

         V = u + at
          t =(v-u)/a

Substitute the value of t in (1)

         S = (v+u)/2 x (v-u)/a
     
        
   
        .....(4)

Question 1:
   A car travels with a uniform velocity of 30m/s for 5s and then comes to a rest in the next 10s with a uniform deceleration.
Find,
a) deceleration
b) total distance travelled.

Solution,
a) using, V = u + at
                 Deceleration= -a
                 0 = 30m/s - a(10)
                 10a = 30
                     a = 3m/s/s


b) Let, "Stage A" be the period before          deceleration.
              "Stage B" be the period after deceleration.

At Stage A,

      U= 30m/s
      t1= 5s
      S1= Distance travelled at stage A  ?
Using,
      From the V-T graph,
  Initial Velocity (U) = S1/T1

       S1 = ( 30 x 5) m

       S1 = 150 m



 At Stage B,
     
          U= 30 m/s
          V = 0
          T2 = 10s
          S2 = Distance travelled at stage B ?

Using,       
             
           0 = (30)(30) + 2(-3)(s2)

          900 = 6(s2)

          S2 =150m

Total distance travelled (S) = S1 + S2
             
                                              S = (150 + 150) m/s
                         
                                               S = 300m.

Question 2:
     A bus moves from rest with an initial acceleration of 2m/s^2 for the first 10 s. It then accelerates at a uniform rate of 1m/s^2 for another 15s. It continues at a constant speed for 70s and finally comes to a rest in 20s by a uniform deceleration. From the graph calculate.
I)Total distance travelled
II) Average speed for the journey
III) Average retardation as it is brought to rest.
IV) Maximum speed attained by the motion.

Solution,

    From the V-T graph

I).  for the first 10s,
                   U= 0

                   a = 2m/s/s
                 
                    t1 = 10s

   Velocity (V)= u + at

                    V = 0 + (2)(10)
                    V = 20m/s
         Distance (S1) = [(v +u)/2] t

                  S1 = [ (20 +0)/2] x 10
                       
                  S1 = [10 x 10] = 100m

   
For the second 15s
                   U= 20m/s
                 
                    t2 = 15s
     Velocity (v)  = ( 20 + 15) m/s
                         V = 35 m/s
 
   Distance (S2) = [(v +u)/2] t
 
                       S2 = [ (35 +20)/2] x 10
                       
                        S2 = [41.25 x 10] = 412.5m



For the third 70s,
                        V = constant at 35m/s
                         t3 = 70s

                        V =  S3/t3
       
                        S3 = (35 x 70) m

                        S3 = 2450m




For the last 20s (Retardation or deceleration).

                        V = 0

                        U = 35m/s

                        t4 = 20s

             S4 = [(v +u)/2] t4
 
                        S2 = [ (0 +35)/2] x 20
                       
                        S2 = [35 x 10] = 350m

Total distance travelled(S)= S1 + S2 + S3 + S4
   
                         S = [ 100 + 412.5 + 2450 + 350]

                          S = 3312.5m

II) Average velocity =  S / T
     
                          T = [ 10 + 15 + 70 + 20] s
   
                          T = 115s
               
                           V = 3312.5/115 = 28.8 m/s

Average velocity spent for the journey = 28.8m/s

                       
III) Average Retardation = (v-u)/t4
       
                                V = 0
                                U = 35m/s
          AR = (0 - 35)/20
          AR = 1.75 m/ s (square)

 Average Retardation as it's brought to rest = 1.75m/s^2


        Motion under gravity
 Motion under the influence of gravity is based on acceleration due to gravity(g)  of a free falling object and  +/- g sign conventions.

Formula

   
 
 

Question 1
        A cricket ball is thrown vertically upwards with an initial velocity of 40m/s . Find,
I) it's velocity after 3s
II) Maximum height attained and the time it
III) The total time taken for the ball to return to the ground again.

Solution,
 
I) V = u - gt
     V = 40 - 10 (3)
     V = 40 -30 = 10m/s

II) using,
   
       V = 0
       U = 40m/s
        g = 10m/s/s
  From formula,

         (40)(40) = 2 (10) h

              1600 = 20 h

                  h =80 m
     
           
 Therefore,            
            80 = 40t -  5t^2 ( it is now a quadratic equation)

            16 =  8t - t^2

           t^2 - 8t + 16 = 0

           (t - 4)(t - 4) = 0
     
             t = 4s


Conclusion

    Basic equations of motion was broken down here. If you have any questions, suggestions or feedback write them below. All comments are appreciated.

Save this image below for future reference.


All the equations of motion








       

       

   

         





Read More
//// Leave a Comment

Physics: All about Acceleration due to gravity (g)

acceleration due to gravity value on earth different on other planets

Acceleration due to gravity

Acceleration due to gravity (g) is known when a free falling object from a certain is attains a final velocity. Then take g=9.81m/s/s because this will give you a more accurate answer.The second decimal place in this numerical value are dependent primarily upon on altitude, that is why g = 9.8m/s/s sometimes. Take it as 9.8 or 10m/s/s if you are given in the question.

Read More

Thursday, 6 October 2016

//// Leave a Comment

Physics: Motion, types, Terms and terminologies.

Basic knowledge of motion



Motion

This is the change in the position of a body in respect to time. It also involves how things move and what makes them to move.

Read More

Wednesday, 5 October 2016

//// 1 comment

Physics: Fundamental, derived quantity, Units, and Dimensions.

Fundamental Vs Derived quantity 
Basic fundamental and derived quantities



Fundamental quantities 

 These are independent quantities with units. The dimension of a physical quantity indicates how it is made up in terms of S.I base quantity. 

In other words, the physical quantities is said to have been expressed in terms of fundamental units [Length (L), Mass (M), Time (T), kelvin (k), mole etc].



Quantity Dimension

length         L
Mass          M
Time           T
Kelvin        K
Mole          m



Derived quantities: 

  These are obtained by some simple combinations of the fundamental quantities and units. 

They are thus, dependent on the fundamental quantities and units. Example of the derived quantities, their derivation and their units are summarised in the table below:




Derived quantity
Derived unit
Dimension
Area  (length x breadth)
m^2
L^2
Volume(length x breadth x height)
m^3
L^3
Density (Mass/volume)
kg/m^3
M/L/L
Velocity (Displacement/time)
m/s
   L/T
Acceleration (Velocity/time)
m/s/s
L/T/T
force (Mass x acceleration
Newton (N)
ML/T/T
Energy & work (force x distance).
joules
ML^2/T/T
power (work/time)
joules/s
ML^2/T/T/T
Momentum (Mass x velocity)
kg m/s
ML/T
Pressure  (force/area)
N/m^2
?
Frequency (no of oscillation/time)
1/s
   1/T



Watch video 





Example 

What is the dimension of EMF? 


EMF(Electromotive Force) is a derived quantity. It is work done by the chemical force to move unit positive charge from negative terminal to positive terminal of the battery.
EMF = Workdone / charge
Work=Force * displacement
=MLT^-2 * L =ML^2T^-2
Charge=Current * time
=IT
Now,
Dimensional formula of
EMF=Work/charge
=ML^2T^-2 / IT
=ML^2T^-3I^-1


Exercise:

What is the dimension of pressure?

Solution 
Watch how to derive the dimension of Pressure. 






Get more Info:











Conclusion

A  derived quantity is derived from fundamental quantity, simple and short. I hcomments article was helpful. If you have any questions or comments, please don't hesitate to write it in the comments section. All comments are appreciated. 

DOWNLOAD THE FULL ARTICLE

Read More

Tuesday, 4 October 2016

//// Leave a Comment

Physics: Mass and Weight, relationship, differences and related questions



mass and weight differences and relationship


Mass

A mass of a body is the quantity of matter contained in that body. It is a scalar quantity I.e. it has magnitude but no direction. The unit of mass is kilogramme (kg).



Read More