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
Gravity is a force of attraction. The exact reason why it pulls all things is yet to be ascertained by scientists.
Gravity is defined a natural force that pulls (or attracts) a body towards the center of the earth. It is also defined as a force that pulls a physical body with a lesser mass to another body with a greater mass. You may think of gravity as a magnet that pulls together anything that has mass.
Mass is defined as the quantity or amount of matter a body has.
The earth is governed by the force of gravity and that’s why everything present on it, including humans, plants, animals and even air is always drawn towards it. To overcome gravity, one will need some form of force greater than gravity in order to pull oneself away from the earth.
Please read on the importance of gravity here.
As an instance, the earth as we know is spherical in shape and held in space. Also, all humans live on a constantly rotating earth (and not inside the earth). Since we live on a spherical earth held in space, how come humans are yet to fall off the constantly rotating earth?
Well, the answer is gravity. Even if we attempt to jump off the earth into space, the force of gravity present on earth will still pull us down. In fact, in order to leave the earth; there has to be a force stronger that gravity; which must be applied to whatever is attempting to leave the earth. For this reason: 'whenever one jumps, a certain amount of force must be applied by that person. However, gravity still return the person back to earth because the applied force had been exhausted.
Please read on the concepts of force and motion here.
Planes and jets leave the earth and remain in the atmosphere simply because a certain amount of force is constantly applied to it; and this force is always stronger than gravity throughout its flight.
Please read the interesting facts on gravity here.
Also, gravity holds the air we breathe towards earth. As one moves away from the earth, the air becomes thinner until it vanishes. This is why astronauts wear oxygen mask whenever they are in space.
You can read on the layers of the atmosphere here.
It is important to understand that gravity is not even (the same) all round the surface of the earth. It is slighter stronger on earth surfaces with a greater mass underground than those with lesser masses.
The gravity on earth has also got some impact on its satellites. Think of a satellite as either a machine or moon or planet that revolves around a larger body.
The earth has got one natural satellite (that's the moon) and many artificial satellites. Interestingly, the earth is also a satellite to the sun. This is true because it revolves round the sun.
The earth's natural satellite (moon) constantly revolves around the earth because the earth draws it closer to itself via the force of gravity. Even the moon has its own force of gravity. In short, everything in the universe have got gravity acting on them and that is why they are all held in space. This will include all the planets, the moon, sun, stars and other components of the solar system.
Please read on the solar system here
The larger the size of an object, the greater its force of gravity. Gravity is therefore affected by the size and closeness of objects.
Since the earth is larger than the moon, it will have a greater gravitational force than the moon. We will be attracted more to the earth than we would on the moon if we were astronauts on the moon. This implies that we will weigh differently on both places. For this reason, our weight will also vary on the various planets (because they are of different sizes). This is shown in the diagram below:
Weight depends on the degree at which the gravity on earth or moon or another planet pulls an object while the mass of any object or body will always remain the same (constant) since it is the amount or quantity of matter in the body.
We can escape earth’s gravitation pull by travelling far away from the earth into space. Since the space is somewhat empty and has no gravity, we will end up floating in it because nothing attracts (pull) us in space. For this reason, astronauts will float in space as a result of a condition termed weightlessness. In simple terms, weightlessness results from a lack of gravity.
It is not compulsory that the force of gravity must pull everything into contacting themselves. It can also bring objects close to one another and not necessarily into contact. For instance the moon, sun, stars and other planets of the solar system does not make contact with the earth; rather, they have varying proximity to it as a result of gravity.
Please read on the planets of the solar system and their characteristics here
Other planets have their moons and they revolve around them. This is also a result of gravity that exists between these planets and their respective moons.
The scientists Sir Isaac Newton and Albert Einstein have been credited for their insight and explanations on gravity.
Please read on the basic and fundamental concepts of physics here.
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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