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
Let's begin by considering the instance below:
If we have water of 100OC in an aluminium cup whose temperature is the same as that of its surrounding; let’s say 22OC; We will observe the followings:
Note: OC = degree centigrade; and it's a unit of temperature.
Please read on fundamental and derived units here.
For now, think of temperature as the degree of hotness or coldness of a substance or an object with reference to some standard value.
From the above instance, it can be deduced that the heat present in the water molecules are first transferred to the aluminium cup and subsequently to the surrounding.
Heat from water >>> Aluminium Cup >>> Surrounding
Meanwhile, understand that aluminium is a metal; and metals are good conductors of heat.
Please read on the physical properties of metals here.
Eventually, the system and the surroundings will reach the same temperature; and the heat transfer ceases. It is at this point, that the water, aluminium cup and the surrounding are said to have reached a thermal equilibrium. This concept of thermal equilibrium is a function of the zeroth law of thermodynamics.
Please read more on heat transfer by conduction here.
Please read on the zeroth law of thermodynamics here.
Although the surrounding receives heat from the water and aluminium cup, it is noteworthy to state that the surrounding's temperature may remain approximately unchanged for the following reasons:
Heat is never lost because it is a form of energy. Instead, it will be transferred according to the first law of Thermodynamics which states that:
Energy can neither be created nor destroyed but can be transferred from one form to another. You can read on food chain here.
From the above explanations, the transfer of energy (heat energy in this case) from the water to the aluminium cup and finally to the surrounding is referred to as heat.
Heat can simply be explained as an energy that results from the transfer of energy from an object or substance or system with a higher temperature to another with a lower temperature.
Let us consider a reverse instance with regards to heat:
Now, imagine that a cold bottle of water is brought out of the fridge into the kitchen. Assuming the temperature of water is 3OC while that of the kitchen environment is 22OC; the followings will occur:
Meanwhile, understand that at no point did the coldness of the bottle or water escaped into the surrounding. Instead it is the temperature of the room that actually caused an increased temperature of the bottle and water (inside the bottle).
In fact, if the temperature of the room was higher than 22OC, heat transfer will be achieved at a much rapid rate; that is, the rate at which the temperature of the water and bottle increases will be faster.
Since heat energy is being transferred from the kitchen surroundings to the bottle and then into the water, we can therefore conclude that heat will always be transferred from a higher region to a lower region until equilibrium is attained.
Heat is never static. It is always transferred and thus; an object will increase its temperature by gaining heat energy from its surroundings while another object simultaneously (at the same time) decreases its temperature by losing its heat energy to the surroundings. For this reason, we may also define temperature as:
The measure or ability of an object or substance to transfer heat energy to another object or substance.
The higher the temperature, the greater the ability of an object or substance to transfer heat. Conversely, the lower the temperature, the greater the tendency of an object to receive the transferred heat.
The point is: 'for heat to be transferred, we must have systems or objects or substances with varying temperatures.
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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