Tag: physics

In everyday life, we walk, drive cars, and lift objects. All these tasks need a force to be performed. So, it is necessary to understand this force scientifically. This force was described scientifically by Isaac Newton. He described the force and its relationships in his laws that are known today as the Newton’s Laws of Motion.

First Law of Motion

The first law states that an object in motion will continue to move with same speed in the same direction until another force acts on it. Furthermore, an object which is at rest (not moving) will not move until some external force acts on it.

You may be thinking, how this is possible. Because as you kick a ball, it will immediately start to slow down and will come to rest at a distance. This happens because of air friction. As you kick a ball, frictional forces immediately start to oppose the motion of the ball until it comes to rest.

Second Law of Motion

The Second Law states that force is equal to mass times the acceleration. Let’s say it in other words, the more force is applied to an object the more acceleration will be produced in it. As a result, the object will speed up faster. For example, if you hit a ball harder, it will go faster and farther.

The Second law of motion can also be defined in the mathematical form. It is defined as, F = mass * acceleration.

F = m*a; m is the mass and “a” is the acceleration

Third Law of Motion (Every action has reaction)

You may be familiar with the statement of this law which states that “every action has equal and opposite reaction”. In other words, each applied force also has the opposing force, which has the same magnitude of applied force but in opposite direction. For example, when you kick a ball with 10 N force, your feet will also experience the same 10 N force from the ball.

Facts

• First law of motion also tells us that, mass has a resistance to change in motion. This resistance is called inertia.
• Sir Isaac Newton is also the founder of Calculus; a branch of mathematics which deals with the rate of change.
• An object in motion experiences friction from the ground and air. Friction also helps our cars to slow down, when the brakes are pressed.

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.

Solution:

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.

Facts

• 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.

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

Facts

• 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.

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:

Solution:

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

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

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.

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

Facts

• 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.

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.

Solution:

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.

Facts

• 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.