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
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
FA = -FB
FA is the action force while FB is the reaction force.
The above statement expresses _____.
A. Force and Acceleration
B. Force and Gravity
C. Force and Momentum
D. Newton's first law of motion
E. Newton's second law of motion
F. Newton's third law of motion
A natural force that pulls a body towards the center of the earth is termed _____.
A. Centripetal force
B. Centrifugal force
C. Black hole
D. Average acceleration
A Greek letter that expresses density is _____.
A glass of water has a higher density than an exact glass of oil.
An 🍎 apple 🍎 falling from a tree has an unbalanced force.
Force is a quantity measured in _____.
D. Meter per second square (ms-1)
Motion can be defined as a change in the position of an object with reference to time.
We have 3 laws of motion as postulated by Sir Isaac Newton in 1687. These are:
Newton's First Law of Motion
Note: A good knowledge on the concept of force will aid you to better understand the above laws.
Also known as 'law of Inertia', Newton’s first law of motion states that:
An object at rest will continue to stay in its state of rest or if the object is in uniform motion, it will continue to move in a straight line unless an external force acts on it.
When no force is applied to a body, the tendency or outcome of the body to remain in a state of rest or in a uniform linear motion is known as inertia.
The concept of inertia implies that an object at rest will continue to remain in a state of rest while another in uniform motion will keep moving in a straight line as far as the object isn't acted upon by a force.
You can think of inertia as being resistant to change. Meanwhile, understand that inertia is a property of matter.
It was Newton’s first law of motion that showed the presence of inertia in a body at rest (or in a body moving with a constant velocity).
Recall that matter is anything that has mass and occupy space. Also, mass is a measure of inertia. In this regard, the larger the mass of an object, the more inertia the object would have.
In summary, the law of inertia which is a reference to Newton’s first law of motion summarizes what force can do in relation to mass.
Newton’s second law of motion states that the rate of change of momentum is proportional to the applied force and will take place in the direction of that force.
You can think of momentum as mass in motion; that is, the quantity of motion a moving body has. You may have heard a commentary on a football match stating that a team has gained momentum. This will imply that the team is on the move or pressing high.
Momentum is the product of mass and velocity.
When we apply the second law of motion to reality, it will help us determine the amount of force needed to make an object move or stop.
The second law is applied in various field of sports including football, basketball and cricket.
In the game of cricket, the players will usually pull back their hands when catching the ball. This is so because pulling back the hands increases the time of contact with the ball, thus resulting in less jerk from the motion of the caught ball.
Through Newton’s second law of motion, we are able to define an absolute unit of force which remains constant under a moving condition.
Also, the second law of motion gives us the operational definition of force as the rate of change of momentum with time.
Newton's third law of motion states that action and reaction are equal and opposite.
The third law can also be stated thus: 'To every action, there is an equal and opposite reaction.
Consider the instance below:
When a boxer blows a wall, he will in return feel a reverse force on his hands.
Although the boxer exerts a force on the wall (in the above instance), the wall in return exerts an opposite force on hands of the boxer. Based on this fact, the boxer may feel some pain on his hands depending on the nature of the wall and the degree of force exerted on the wall.
Also, playing a football match without boots might get you injured when you kick a player. This is so because there is a reverse force from the kicked player.
Newton’s third law exists on everything that has mass. It is also seen and encountered in wrestling matches.
According to the third law of motion, if a body 'A' exerts a force FA on another body 'B', body B will in return exert an equal and opposite force FB on body A. The forces FA and FB are therefore equal in magnitude but opposite in direction.
We can therefore write the above expression as:
FA = -FB
From the above, FA is the action force while FB is the reaction force.
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Amazing facts in Physics
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 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
The earth is governed by the force of gravity and that’s why everything present on it (humans, plants, animals and even air) is always drawn towards it. You will actually need some form of force greater than gravity in order to pull yourself away from the earth.
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 is needed to be applied by that person. However, gravity still return the person back to earth because the applied force had been exhausted.
The larger the size of an object, the greater it’s 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 more attracted on 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’s the amount or quantity of matter in the body.
To better understand the Zeroth Law of Thermodynamics, we need to know what thermal equilibrium is. This is explained below:
Two bodies A and B are said to be in thermal equilibrium if each body can transfer heat to each other when placed closed together but ended up not transferring any heat to each other.
This will mean that both bodies are at equal temperature.
Now, according to the zeroth law, assuming we have three bodies namely X, Y and Z:
If X = Y and Z = Y, then X = Z
From the above expression, it will be observed that: if X and Y are in thermal equilibrium and Z and Y are in thermal equilibrium, therefore, X and Z must be in thermal equilibrium too.
So we can see that according to the zeroth law, temperature is a quantity worth measuring.
It can therefore be said that temperature is the quantity that remains constant (the same) for all systems in thermal equilibrium.
Consequently, the zeroth law of Thermodynamics states that if two separate bodies are in thermal equilibrium with another body, then they are also in equilibrium with each other