Alfred Ajibola
- Tue, 10th September, 2019 @ 4:25 PM
Topics in Physics
Derived Units: Similarities and differences with fundamental units Gravity: Facts on Gravity Relative Density of Substances and Specific Gravity Types of Heat Transfer: Conduction Types of Heat Transfer: Convection Types of Heat Transfer: Radiation Physics Scheme of Work, SS1, First Term Physics Scheme of Work, SS1, Second Term Physics Scheme of Work, SS1, Third Term Velocity and Acceleration Newton's Laws of Motion Importance of Gravity What is Density? Density of various substances Concepts of Force and Motion in Physics Motion and Speed in Physics Concept of Heat Transfer Concepts of Heat and Temperature Gravity on the solar system Zeroth Law of Thermodynamics: Thermal Equilibrium Fundamental Quantities and Units in PhysicsAcademic Questions in Physics
Which of the following is a fundamental quantity?
A. Luminous Intensity
B. Area
C. Volume
D. Velocity
E. Concentration
F. Acceleration
An object at rest will temporarily stay in its state of rest, and if the object is in uniform motion, it will temporarily move in a straight line, unless an external force acts upon it.
The above statement refers to Sir Isaac Newton's first law of motion.
A. True
B. False
Which of the following statement is incorrect concerning gravity?
A. The force of gravity is generally considered the strongest force among the four forces that govern the universe
B. Your weight changes as you travel away from the earth
C. If we dig the earth until we get into its center, we will have no weight as a result of lack of gravity
D. Gravity prevents us from falling off the constantly rotating earth
E. If a hammer and a feather are dropped simultaneously in a vacuum, they will both land at the exact same time as a result of gravity
F. Weight is always a function of gravity
Sir Isaac Newton was hit by an apple when he pondered on force, motion and gravity.
A. True
B. False
The movement of gaseous particles through a tiny hole is termed _____.
A. Osmosis
B. Diffusion
C. Effusion
D. Infusion
E. Defusion
F. Gaslusion
A lighted bulb transfers heat through a process termed _____.
A. Conduction
B. Convection
C. Radiation
D. Oxidation
E. Reduction
F. Electrical Induction
A measurement of how much the velocity of an object changes with time is termed _____.
A. Displacement
B. Acceleration
C. Speed
D. Momentum
E. Velocity-Time graph
F. Average velocity
Which of the following differentiates velocity from speed?
A. Distance
B. Time
C. Momentum
D. Inertia
E. Direction
F. Distance and Time
Density relates to the mass and weight of substances. This is so because equal volumes of different substance have got different masses and weights.
For instance; a box containing iron will be heavier (have a higher density) when compared to a similar box containing wood. This is true because wood has a lower density.
Similarly, a glass of water will have a higher density than an exact glass of oil. (Water has a higher density in this case). For this reason, oil floats on water.
You can read on separation of mixtures (water and oil) here.
The difference in the density of various substances is simply a result of the different atoms that make them up. For instance; water (H2O) is made up of hydrogen and oxygen atoms in the ratio of 2:1 and this is different from the constituent atoms making up common salt or sodiun chloride (NaCl). The constituent atoms in NaCl are sodiun and chlorine respectively.
Please read on periodic table and classification of elements here.
Density is defined as the mass of a unit volume of a material or substance.
The principle of density was determined by a Greek scientist named Archimedes.
The formula for density is shown below:
ρ = M/V
Where:
ρ = density
M= Mass
V = Volume
Please read more on relative density and specific gravity of various substances here.
It is worthy of note to state that 'rho' is a Greek letter that expresses ρ (density).
The Standard International (SI) unit for density is kilogram per cubic metre (Kg/m3).
You can read on fundamental and derived units here.
The table below shows various substances with their densities:
|
Substance |
Density (Kg/m3) |
|
Helium |
0.179 |
|
Air (1atm and 20oC) |
1.20 |
|
Bamboo Wood |
400 |
|
Ethanol |
810 |
|
Methylated Spirit |
800 |
|
Benzene |
900 |
|
Paraffin Wax |
900 |
|
Ice |
920 |
|
Water (Fresh Water) |
1000 |
|
Sea Water (Saline/Salt Water) |
1030 |
|
1600 |
|
|
Glass |
2600 |
|
Aluminium (Al) |
2700 |
|
Zinc (Zn) |
7100 |
|
Iron (Fe) |
7900 |
|
Copper (Cu) |
8900 |
|
Lead (Pb) |
11300 |
|
Mercury (Hg) |
13600 |
|
Gold (Au). |
19300 |
|
Platinum (Pt) |
21500 |
Notice from the table that helium has a lower density than air and that's one reason why it's used in filling balloons.
Having an understanding on density offers a convenient means of deriving the mass of a body from its volume. Similarly, when we know the mass of a body, we can derive it's density.
Below are the derivation steps:
Mass = Volume x Density (M = Vρ)
Volume = Mass divided by the Density (V = M/ρ)
To get the weight of a body, we will need to multiply its mass by the acceleration of gravity.
Please read more on gravity here.
A common application of density is seen in the way at which different materials interact with each other. For instance; a wood may float on water while an iron may sink in it.
Also, balloons will float in air because it's filled with helium gas which is much lighter (has a lower density) than air. Conversely, a nylon filled with sand will not float in air.
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Amazing facts in Physics
Marie Curie was the first person ever to win two Nobel prizes. She won her first Nobel price for physics in 1903, and the second for chemistry in 1911 for her work on radioactivity.
The hottest temperature ever recorded occurred in Furnace Creek Ranch, Death Valley, California, USA, at 56.7oC or (134oF) on July 10, 1913
A medium-sized cumulus cloud has a weight of about 80 adult elephants.
You can think of cumulus cloud as a detached, individual, cauliflower-shaped cloud often seen in fair weather conditions
The reason the Leaning Tower of Pisa is tilted is the same reason it's still standing
One quarter of an apple is filled with air and that's why they float in water
The Nobel price was named after its founder, Alfred Noble. He is a Swedish, born on October 21, 1833; and was the inventor of dynamite. He was also a a famous scientist and a successful business man.
Glass balls bounce higher than rubber balls
Every planet has its own unique gravitational force. For instance, Mars has a gravity of 3.711 m/s2 while earth’s gravitational force is 9.807m/s2.
When two metals are put together in space, they will stick together as if they are welded. This phenomenon is called cold welding
The fastest animal on land is cheetah. It can reach a maximum speed of about 113km per hour.
Notable points in Physics
The Standard International (SI) unit for density is kilogram per cubic metre (Kg/m3).
The table below shows various substances with their densities:
|
Substance |
Density (Kg/m3) |
|
Helium |
0.179 |
|
Air (1atm and 20oC) |
1.20 |
|
Bamboo Wood |
400 |
|
Ethanol |
810 |
|
Methylated Spirit |
800 |
|
Benzene |
900 |
|
Paraffin Wax |
900 |
|
Ice |
920 |
|
Water (Fresh Water) |
1000 |
Force can be balanced or unbalanced.
When forces from different directions act on an object and consequently bring about the object's motion, then such forces are unbalanced.
Conversely, if theses forces bring about zero motion (static position or no movement) on the object of reference, then it's a balanced force.
In summary,
An apple hanging on a tree (without any form of movement) has a balanced force.
An apple falling from a tree has an unbalanced force.
If one covers a distance of 10,000 meters in 50 seconds and another covers the same distance in 5,000 seconds, we can conclude that the first person has a greater speed because he covered the same distance at a lesser time.
Speed is defined as distance travelled per unit of time. It can also be defined as the rate of change of distance.
Speed = distance/Time
Speed is a scalar quantity since it has only magnitude. Speed does not have a direction.
In physics, motion is defined as a change in the position of an object with reference to time.
Although we sometimes sit or stand in a fixed position, that doesn’t mean motion isn’t taking place. The fact that the earth is constantly rotating implies that we are indirectly moving along with it. We can thus say that motion can be relative to some frame of reference.
In the above paragraph, the earth (constantly rotating along its axis) is our frame of reference and everything present on earth is in motion (with regard to earth as a frame of reference).
Heat is a form of energy. It cannot be lost according to the first law of Thermodynamics; rather it will be transferred. The first and second laws of thermodynamics are stated below:
Energy can neither be created nor destroyed but can be transformed or converted from one form to another.
1st law of thermodynamics
In the course of energy transfer, some energy is lost in the form of heat to the surroundings.
2nd law of Thermodynamics