Forces are an external cause that makes a body move, stop, and increase its velocity and other. There are various types of forces in physics and they are generally classified into two categories that are, Contact Force and Non Contact Force.
Contact Force
A contact force is any force that requires a contact to occur or in simple words, we can say that it arises during the motion of one object over the surface of another. Contact forces are generated only when in contact and are responsible for the most visible actions between macroscopic collections of matter. Pushing a car up an inclined surface or kicking a football across a room or in a playground or pushing any block from one place to another place or shifting large blocks from one place to another are some everyday examples where contact forces are at work.
The various types of contact force are shown in the image added below,
Frictional Force
Friction is a force that acts between two surfaces in contact and opposes their motion. It occurs when surfaces slide, roll, or move against each other. Friction always acts in the direction opposite to the motion of an object, which is why it slows moving objects down.
Examples of Friction
- Friction helps us walk without slipping because it acts between our shoes and the ground.
- Car tyres use friction to prevent skidding on roads.
- Athletes wear spikes in their shoes to increase friction and improve grip.
- Cricketers use gloves to increase friction and prevent the bat from slipping from their hands.
Formula
The force of friction is calculated by using the following formula
F = μN
where,
- F is Force of Friction
- μ is the Coefficient of Friction
- N is the Normal Reaction Force
Muscular Force
Muscular force is the force produced by the muscles of the body to push, pull, lift, or move objects. It is a contact force that helps us perform daily activities such as walking, running, lifting, and bending. Without muscular force, humans and animals would not be able to carry out physical movements.
Examples of Muscular Force
- Walking, running, and jumping require muscular force.
- Lifting a book or carrying a bag involves the use of muscles.
- Getting up from a chair or crossing legs uses muscular force.
- In a tug of war, the team applying greater muscular force pulls the rope towards itself.
- Pushing or pulling heavy objects also depends on muscular force.
A man pushing a block is an example of muscular force because the force applied comes from the muscles of his body.
Normal Force
The reaction force applied by any object that balances the gravitational force of the Earth is called the Normal force. This force is called the normal force as it is always applied to the normal of the surface. Suppose we observe a bag lying on a thetable then the gravitational force acts on the bag in the downward direction this force is balance by an equal and opposite force called the Normal force that acts normal to the surface of the bag.
Applied Force
The force applied to a person or an object that changes the speed, shape, and direction of the object is called the applied force. This force is the force of push or pull that is applied to an object.
Tension Force
The force experienced in the string of a stretched string is the example of the Tension force. Suppose a mountanier climbs a mountain using a rope then his/her weight is balance by the tension force in the string.
Spring Force
The force of compressed or stretched string is called the spring force. When we stretch or compress a string its stores some energy and this energy is responsible for the spring force.
Air Resisting Force
The force experience by any object moving in the air is called the air resistance force. This is a type of Frictional force, suppose we drive our bike on a windy day against the wind then the wind apply a resisting force on our bike called the air resisting force.
Non-Contact force
A non-contact force is a force that acts on an object without coming physically in contact with it. Gravity is the most familiar non-contact force, which confers weight. In contrast, a contact force is a force applied to a body by another body that is in contact with it or in other words, Forces that arise without the contact of 2 or more objects involved. The types of non-contact forces are:
- Gravitational Force
- Magnetic Force
- Electrostatic Force
- Nuclear Force
Gravitational Force
Gravity, also called gravitation, in mechanics, the universal force of attraction acting between all matters. All bodies have a weight on Earth, or downward force of gravity, proportional to their masses. Gravity is measured by the acceleration that it gives to freely falling objects. In other words, Gravitational force is a force exerted by the earth on all objects on it. Gravitational Force surrounds us everywhere we are. It is present when we are sitting, playing, walking, throwing, and everywhere. Not only Earth but any other massive celestial body exerts a gravitational pull. It can be greater or equal to or lesser than Earth’s gravitational force, but it is present to some extent. Since the bodies with a greater mass attract everything towards us hence there is a gravitational pull on anywhere we are on if it has a mass much greater than our weight.
Example of Gravitational Force
- When a ball is thrown up, it falls to the ground because of gravitational force.
- Water always flows downwards because of gravitational force.
- When we throw an apple up it comes down because of gravitational force.
- Any fruit falls in a downward direction always it is also due to gravitational force.
Gravitational Force Formula
It is denoted by the equation,
F = G(m1m2)/r2
where,
- F is Gravitational Force
- G is Universal Gravitational Constant
- m1 and m2 are masses of two Bodies
- r is the distance between Two Masses
Magnetic force
Attraction or repulsion that arises between electrically charged particles because of their motion is called magnetic force. The magnetic force is a consequence of electromagnetism, one of the four fundamental forces of nature, and is caused by the motion of charges. Â In simple words, two objects containing charge with the same direction of motion have a magnetic attraction force between them. If the two objects have opposite charges then they repel each other.
Magnetic Force Formula
It is calculated by the given formula,
F = qVB sin θ
where,
- F is the Magnetic Force
- q is the Charge of Moving Particle
- B is Magnetic Field
- θ is angle between Velocity and Magnetic Field Vectors
Electrostatic Force
The force caused due to electric charges in an attractive and repulsive manner between the particles is called electrostatic force. The force between stationary charged bodies is conventionally known as the electrostatic force. It is also referred to as Columba’s force. In simple words, Electrostatic force is the force that exists between electrically charged particles or objects at rest.
Examples of Electrostatic Forces
Various examples of the electrostatic force are,
- When we rub a small paper piece with the oil in our head with the help of a comb it attracts the paper as shown in the image added below, this is because of the electrostatic force.
- Balloons always get attracted towards another balloon when one of them is rubbed with hair.
- When we iron silk clothes they often cling together after some time due to electrostatic charges.
- Lightning is also considered an example of electrostatic force.
Electrostatic Force Formula
Electrostatics force is calculated by using the formula,
F = k (q1q2)/r2
where,
- F is the Electrostatic Force of Attraction
- k is Constant of Proportionality
- q1 and q2 are the charges of two Bodies
- d is the distance between the two Bodies
Nuclear Force
The Force experienced inside the nucleus of an atom is called the nuclear force and this force is only attractive in nature. This force is responsible for binding the protons and neutrons of nucleus together. They are one of the strongest force in the universe.
Weak Forces
Forces that are required for the decay of neutrons are called weak forces. The neutron in weak force decay into protons and emit a electron and a antineutrino. The weak force works in even a smaller distance such as 1/10 th distance of the diameter of proton.
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Solved Examples
Example 1: What is the frictional force on an object if the coefficient of friction is 0.50 and the normal reaction offered is 60N?
Solution:
As we know,
F = μN
Given,
- N = 60N
- μ = 0.50
F = (0.5)(60)
F = 30 N
Hence the frictional force is 30 N
Example 2: What is the coefficient of friction if the frictional force exerted is 60N and the normal reaction offered is 80 N?
Solution:
As we know,
F = μN
Given,
- N = 80 N
- F = 60 N
μ = F/N
μ = 0.75
Hence, the coefficient of friction is 0.75
Example 3: What is the normal reaction if the frictional force exerted is 50N and the coefficient of friction is 0.25?
Solution:
As we know,
F = μN
Given,
- F = 50 N
- μ = 0.25
N = F/μ
N = 50/0.25
N = 200 N
Hence, the normal reaction offered is 200 N
Example 4: What is the gravitational force on two bodies of masses 2kg and 4kg respectively and the universal gravitational constant (G) beingwith the separation between them being 4 m?
Solution:
As we know,
F =G(m1m2)/r2
Putting the values from the question we get,
F = (6.6 × 10-11 × 4 × 2)/42
F = 3.3 × 10-11 N
Example 5:What is the gravitational force on two bodies of masses 4 kg and 6 kg respectively and the universal gravitational constant (G) beingwith the separation between the two bodies being 2 m?
Solution:
As we know,
F =G(m1m2)/r2
Putting the values from the question we get,
F = (6.6 × 10-11 × 4 × 6)/22
F = 39.6 × 10-11 N
Example 6:What is the electrostatic force between two charges of charge 4C and 5C which are at a distance of 4m with constant of proportionality 1?
Solution:
As we know,
F =K(q1q2)/r2
Putting the values from the question we get,
F = (1 × 4 × 5)/42
F = 1.25 N
Example 7: What is the electrostatic force between two charges of charge (-3C) and (-6C) which are at a distance of 4 m with constant of proportionality 1?
Solution:
As we know,
F =K(q1q2)/r2
Putting the values from the question we get,
F = {1 × (-3) × (-6)}/42
F = 1.125 N
Example 8: What is the magnetic force exerted by a charge of 3 C moving with a velocity of 6m/s in a magnetic field of 6 T and the value of sin θ = 1/2?
Solution:
Magnetic forces can be calculated by the following equation
F = qvBsinθ
Given,
- q= 3C
- B= 6 T
- sin θ = 1/2
- v= 6m/s
Putting the values we have,
F = 3 × 6 × 6 × 1/2
F = 54 N
Hence the magnetic force is 54 N
Example 9: What is the magnetic force exerted by a charge of 4C moving with a velocity of 8m/s in a magnetic field of 8T and the value of sin θ = 1?
Solution:
As we know,
Magnetic forces can be calculated by the following equation
F = qvBsinθ
Given,
- q = 4 C
- B = 8 T
- sin θ = 1
- v = 8 m/s
Putting the values we have,
F = 4 × 8 × 8 × 1
F = 256 N
Hence the magnetic force is 256 N
