Topics in PhysicsDerived 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 What is gravity? Concept of gravity on the solar system Zeroth Law of Thermodynamics: Thermal Equilibrium Fundamental Quantities and Units in Physics
Academic Questions in Physics
Which of the following is a fundamental quantity?
A. Luminous Intensity
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.
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.
The movement of gaseous particles through a tiny hole is termed _____.
A lighted bulb transfers heat through a process termed _____.
F. Electrical Induction
A measurement of how much the velocity of an object changes with time is termed _____.
E. Velocity-Time graph
F. Average velocity
Which of the following differentiates velocity from speed?
F. Distance and Time
Conduction can be defined as the transfer of heat energy from one point to another through a solid material termed conductor.
You can think of 'conductor' as a solid material through which electricity, heat and sound can flow through. In this regard, metals are generally good conductors.
Please read on the physical properties of metal here.
Let's explain heat transfer by conduction through this simple experiment which you may carry out at home.
The image below shows a simple experiment where heat is transferred via conduction through a thin metallic rod. This thin metallic rod acts as a conductor in this instance.
From the above image, the 'hand' holding the thin metallic rod (conductor) will eventually feel its 'hotness'. This is so because heat (from the candle fire) had been transferred through the thin metallic rod.
Please read on the concept of heat and temperature here.
Heat transfer via conduction is an observable phenomenon during the process of cooking. In this case, the pot (which acts as a conductor here) transfers the heat of the fire through conduction into its contents. As a result, the contents of the pot becomes cooked (or boiled in the case of water).
Similarly, heat from the cooking pot is transferred via conduction to whomever touches it with their bare hands.
Below is another simple experiment on heat transfer via conduction. It can also be carried out at home.
Step 1: Boil three cups of water in a pot. When the water is very hot, put out the gas.
Step 2: Get another pot and fill it with three cups of cold water.
Step 3: Get an iron rod and make both ends of its edge contact both waters, that is: the hot and cold water respectively.
Observation: After we carry out the above procedure, an increase in the temperature of the iron rod will be observed as heat is transferred into the cold water through the iron rod. The iron rod in this instance acts as a conductor and it transfers heat through conduction.
The movement of heat energy in the above experiment will follow the path below:
Hot Water >> Iron Rod >> Cold Water
In the above experiment, it is the transfer of heat energy that brought about an increased temperature in the iron rod and consequently, the cold water; nothing more, nothing less.
Please read on solids and their characteristics here.
Below are some notable points concerning the experiment:
This heat transfer will continue until equilibrium is achieved; that is, the water inside both cups and the connecting iron rod eventually attain the same temperature.
Please read on the zeroth law of Thermodynamics here.
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Amazing facts in Physics
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
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
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:
The temperature of water inside the aluminum cup will begin to decrease from its initial 100OC.
The temperature of the aluminium cup will increase from its previous 22OC.
After some time, the temperature of the water, aluminium cup and the surrounding will become the same.
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.
Eventually, the system (water and aluminum cup) together with the surrounding reaches the same temperature; and the heat transfer ceases. It is at this point that the water, aluminium cup and the surroundings are said to have reached a thermal equilibrium.
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 will simultaneously decrease 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