lifting force

lifting force

What is Force?

Everything you see around yourself is surrounded by forces. These force may be push-pulls or gravitational. Forces can accelerate, slow-down, and change the shape of an object. So, what is the definition of the force? Force is actually an interaction which when applied to an object, changes or tends change it state of motion or rest. In other words, force can bring the objects that are not moving into motion. Similarly, it can bring the moving objects into the full stop.

Force is a vector quantity, that means it requires magnitude along with a direction in which the force is applied.

How is Force Calculated?

Force is measured in newton, abbreviated as “N”. One newton is equal to a force, which when applied to an object having a weight of 1 kg, accelerates it to 1 m/s^2. That means, if you constantly apply one newton force to a 1 kg heavy object, its velocity will increase by 1 meter per second in each passing second until you remove the force.

Force is calculated by using the Newton’s second law of motion:

F = m*a

Here “m” is the mass of the object and “a” is the acceleration of that object.

Example: A bike has a mass of 100 kg which is accelerating with an acceleration of 5 m/s^2. Calculate the force that is acting upon it.


You are given the mass of the bike and acceleration of the bike. Just apply the Newton’s second law of motion.

F = m*a = 100*5 N = 500 N

Types of Force

There are various types of force, according to their nature. Few most familiar types of force are:

  1. Friction: It is the force which opposes the motion of an object. When you kick a box, it will come to rest at a certain It is the friction that is slowing down the box. Friction only acts on the moving objects.
  2. Gravitation: Gravitation is an attractive force that is caused by heavy objects, like planets. This force attracts anything that has mass. You are standing on the Earth due to the gravitational force of the Earth.
  3. Tension: It is the pulling force which is exerted on strings, cables or any similar object like them.


  • Torque is kind of force that rotate or twist the objects.
  • Gravitational and electromagnetic forces don’t need to have a contact with the object for exerting force. They can exert a force on objects which are away from them.
  • Force was described by the Isaac Newton in his law called Newton’s second law of motion.
mass and weight

mass and weight

What is Mass?

Mass is the quantity of matter that is contained in an object. It remains same, no matter where you take the object, either into space or another planet. Because the number of atoms and their density remains same. Mass is measured in kilograms in international standard of units.

How is Mass Measured?

There various methods for measuring the mass of an object. Two of them are described below:

  1. Inertial Mass: It is determined by the resistance of an object to change the state of rest or motion. For example, you have two smaller balls; one is made of plastic and other is made of iron. When you move each of the balls back and forth, you will notice that iron ball takes more effort to move. This is because the iron ball has more mass than the plastic ball.
  2. Gravitational Mass: Anything that has mass exerts a gravitational force on other objects. This gravitational force is measured to find out the mass of an object.

What is Weight?

Weight is actually force exerted by an object under the influence of gravity. Weight depends on the gravitational pull of our Earth. The weight of an object changes with a change in gravitational pull, but their mass remains constant. Weight also depends on the mass; the more mass you have, the heavier it will weigh under the gravity. If you carry an object to the moon, it will weigh much less because the moon has lesser gravity than the Earth. But in space, the weight of the objects will become zero.

How is weight measured?

Weight has the same unit of force; newton. It can be calculated by using the second law of motion.

F = m*a 

Here F is the weight of an object in newtons, and “a” is the gravitational acceleration of the Earth, which is 9.8 m/s^2.

Example: Calculate the weight of an object, whose mass is 100 kg.

Solution: Use the above formula to calculate the weight

F = m*a

Put m = 100 kg and a = gravity of the Earth = 9.8 m/s^2

F = 100*9.8 N = 980 N


  • The weight of the objects can change in different locations of the Earth. Because at some locations, gravity is slightly weaker.
  • A man weighing 100 pounds on the Earth would weigh only 37 pounds on the Mars.
  • Weight and Force are measured in Newtons (N), It is named after Isaac Newton.
accelerating van

accelerating van

What is Acceleration?

Acceleration is the rate of change of velocity. When the velocity of an object is changed, the object is said to be accelerated. During acceleration, the velocity of an object constantly changes.

Acceleration is measured in meter per second squared (m/s^2), which tells us that how much velocity is changing during each second. Acceleration is a vector quantity. It needs direction along with the magnitude to properly define it.

How is Acceleration measured?

Acceleration is measured by dividing the change in velocity with the amount of time.

a = ΔV/Δt = change in velocity / change in time

Example: A car is traveling at a velocity of 50 km/h. Suddenly the driver presses the accelerator to increase its velocity. The velocity of the car than changes from 50 Km/h to 80 km/h in 10 seconds. Calculate its acceleration:


First, find the change in velocity.

ΔV = V2-V1 = (80 – 50) km/h = 30 km/h

The amount of time is already given to you, which is Δt = 10 seconds.

Now find the acceleration.

a = ΔV/Δt = 30/10 m/s^2 = 3 m/s^2


Deceleration is also the acceleration, but instead of increasing the velocity of an object, it decreases its velocity. You may have observed it when a car driver presses brake to slow down the car.

Deceleration is also called the negative acceleration. The method of calculating the deceleration is same as described above, but the sign will be negative.


Gravity is the acceleration caused by planets. It constantly accelerates the objects downward. Our Earth has the gravity of 9.8 m/s^2, means if you drop an object of any mass from a height, its velocity will increase by 9.8 m/s for each passing second.

See the table below to understand, how much velocity of objects increases with each passing second.

Time period Gravity of Earth Velocity
1st second 9.8 m/s^2 9.8 m/s
2nd Second 9.8 m/s^2 19.6 m/s
3rd Second 9.8 m/s^2 29.4 m/s
4th Second 9.8 m/s^2 39.2 m/s
5th Second 9.8 m/s^2 49 m/s

However, there are certain limitations on how fast an object can fall under the influence of gravity. This is because of the air friction due to the atmosphere. Air friction opposes the moving objects in the air and makes their velocity constant at a certain velocity. This constant velocity is known as terminal velocity.

Read more at Gravity


  • Galileo was the first to demonstrate that, if two objects having different weights are dropped from a height, they will reach the ground in same time.
  • Objects with acceleration can’t reach the infinite velocity. The fastest possible velocity is the velocity of light, which is around 299,792,458 m/s.
  • Acceleration is produced by the force on an object.
velocity of car

velocity of car

What is Speed?

Speed is the physical quantity for measuring the motion of a body with respect to a reference. It is defined as, the distance covered in a given amount of time.

For example, a car is traveling 50 km in an hour, then its speed would be 50 Km/h. Speed is a scalar quantity, means it doesn’t need a direction for its representation.

What is Velocity?

Velocity is a little different than the speed. Velocity is a vector quantity, means it requires direction in which the body is moving along with the magnitude.

For example, a car is moving with a speed of 30 km/h in the north direction. Here you are given the direction (north) along with the magnitude which is 30 Km/h. You can say that the speed is the magnitude of the velocity.

How are speed and velocity measured?

Velocity is measured in its standard unit which is meter per second (m/s). But, commonly we use Km/h (kilometer per hour) and mph (miles per hour). Velocity is calculated according to the following formula:

V = Δd/Δt = change in distance/change in time

or in other words

V = distance covered/amount of time

The magnitude of both speed and velocity is calculated in the same. But, velocity should also have a direction to properly define it.

Example: A car is moving towards west. It has covered 150 kilometers in 3 hours. Calculate its velocity.


Distance covered = Δd = 150 km

Amount of time = Δt = 3 hours

Velocity = Δd/Δt = 150/3 = 50 km/h towards west

Instantaneous velocity

When the velocity is measured at any particular time, it is called instantaneous velocity. A car’s speedometer always shows instantaneous velocity. Instantaneous velocity tells us the current speed of an object.

Average Velocity

Average velocity is defined as, the total distance traveled by an object (e.g. a car) divided by the elapsed time.

For example, a car is traveling towards the north has covered a distance of 50 km in two hours. Then, its average velocity during the 50 km route will be V = 50/2 = 25 km/h. It doesn’t mean that the car was traveling all the time with the velocity of 50 km/h. Because there may be need of braking and accelerate the car, so the car may have traveled with different speed.


  • Light has the fastest possible speed. It’s speed is 299,792,458 meters/second or ‎186,000 miles/second.
  • Escape velocity is the velocity, which when an object achieves can escape the gravitational pull of the planets.
  • If you through an object towards the sky with a velocity of 11.2 kilometers/seconds, it will escape the gravitational pull of the Earth, and will never come back.
  • When two objects with different weights are dropped from a height, both objects will hit the ground at the same time with same speed. It was proved by Galileo Galilei.

Friction-forceYou may be listening to the word friction from your childhood that it slows down the vehicles and wear out the machine part. That is true! Friction causes resistance in motion. It is also a force that acts in opposite direction of motion.

When you put a brake on your bicycle, it stops suddenly because you increase the friction between the wheels and road. It is hard to push a box on a cemented surface than a smooth surface because cemented surface causes more friction due to its irregular surface. On the other hand, if you push the same box on a glass table, it will slide very easily because it has a very smooth surface that causes lower friction.

Types of friction

Friction has been divided into 3 types; static friction, kinetic friction, and fluid friction. All the three types of friction act on any object differently. Let’s see!

Static Friction

pushing-box-sliding-frictionStatic friction, as the name suggests occurs between the objects that are in contact with each other but not moving. So, that means if you place a heavy box on a table, will it experience the static friction? No!


OK so, when static friction actually occurs? Static friction will only occur between two static objects that are not moving even when the force is applied on them. For example, When you put a box on the table it won’t experience static friction until you apply a force to slide it but it still doesn’t move, then it is experiencing the static friction. But when you push the box even harder, the box will move. Now the static friction will be converted to kinetic friction.

Kinetic Friction

bicycle-frictionNow it is time learn about the kinetic friction. Let’s start with an example. Suppose you are riding a bicycle very fast. Tell me what will happen when you suddenly stop paddling? You will notice that the bicycle will start to slow down until it comes to stop completely. This is what you might guess, the kinetic friction!

If one object is moving on another object than both objects will experience kinetic friction. Kinetic friction always occurs between moving objects (In our case, the wheels of bicycles and the road). Normally kinetic friction is less than the static friction due to the motion of the objects.

Kinetic friction is further divided into two types.

  1. Sliding friction: When two objects slide on each other, both will feel the sliding friction. Pushing a box and rubbing your hands both are the examples of sliding friction.
  2. Rolling friction: When one object rolls on another object or both are rolling on each other, they will experience rolling friction. It is less than the Sliding friction that is why pushing a weight on wheels is easier than sliding it. The bicycle that you were riding was experiencing rolling friction.

Fluid Friction

coin-droping-in-liquid-fluid-frictionSolids offer two kinds of friction to an object, but there is also another type of friction that is provided by the fluids, e.g. liquids and gases. Let’s see an example to understand the concept more easily.

What will happen when you drop a coin in oily liquid (your cooking oil)? It will sink slowly to the bottom. Can you tell me why? Yes, you guessed correctly. This is because of the fluid friction. The fluid (oil) is resisting the motion of the coin. Fluid friction increases with two things; one is the velocity of an object and other is viscosity (thickness of liquid) of the fluid. The honey is more viscous than the cooking, so it will provide more friction to the coin. Try it!

The importance of Friction in Everyday Life.

  • It helps us to walk on the road. Otherwise, we would skid away.
  • You warm your hand by rubbing them together.
  • We can stop of vehicles suddenly by putting brakes on them.
  • It helps you to hold a pencil or anything tightly. Without friction, the object you hold would easily slip away from your hand.

Why is Friction Avoided?


  • Friction cause wears in the machinery parts. So, we lubricate the machines to reduce friction
  • Our body joints are well lubricated to reduce friction.
  • Reduced fluid friction can increase the mileage of your car. After the speed of 80 km/h, we spend the majority of our fuel to fight friction.