Introduction to Force, Work and Energy
We often use the phrases force, work, energy, and power in ordinary conversation. A teacher instructing a class, a student studying for a test, a mother making meals, and a farmer ploughing the field are all considered to be at work. A person with high stamina or energy can work for lengthy periods of time. In karate or boxing, we talk about forceful punches delivered quickly. In this article, we will talk about force, work and energy and also about the work power energy formulas.
Force and Its Types
A push or pull on an object is referred to as force. Force is utilised not just to move but also to halt an object. Force is used to affect an object's direction and position. It has the ability to change the speed of a moving object.
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There are several types of forces and some of which are explained below:
Muscular Force: It is defined as any force applied by muscles such as the arms or legs.
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Frictional Force: The force exerted when two surfaces come into contact is known as friction. Friction acts on all moving things, however the force of friction always works in the opposite direction to the movement of the body.
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Gravitational Force: The force that pulls objects downwards towards the earth's core is known as gravity. It means all the objects try to move towards the centre of earth when allowed to fall freely.
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Mechanical Force: A mechanical force is defined as a force that involves direct contact between two things and resulting in a change in the state of the objects.
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What is Work?
Work is defined as everything that exhausts us, such as running, writing, art, and so on. The term "work" refers to both mental and physical labour. As a result, work is said to be done when a constant force is given to an object, causing the object to move in the same direction as the force.
The formula of work is given as:
$W=Fd$
Here,
$F$ = constant force
$d$ = displacement of the object
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Energy and Its Types
Energy can be defined as the ability of an object to do work. It is of two types:
Kinetic Energy: It is the energy possessed by an object due to its motion. For example, if a boy is running then it possesses kinetic energy. Mathematically, we can write the kinetic energy expression as:
$K.E.=\dfrac{1}{2}mv^2$
Here,
$m$ = mass of the moving body
$v$ = velocity of the body due to its motion
Potential Energy: The energy of the body possessed by virtue of its position is known as potential energy. Mathematically, we can express the potential energy as
$P.E.=mgh$
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Power
It is defined as the ratio of work done and time. Mathematical, we can write it as
$P=\dfrac{W}{t}$
Here,
$W$ = work done
$t$ = time during which work is done
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Work Energy Principle or Work Energy Theorem
According to this principle, the amount of work done by a body is always equal to the change in kinetic energy of the body. Mathematically, we can write it as
$W=\Delta K=\dfrac{1}{2}mv^2_f-\dfrac{1}{2}mv^2_i$
Here,
$\Delta K$ = change in kinetic energy,
$v_i$ = initial velocity of the body,
$v_f$ = final velocity of the body.
Solved Questions
What are the units of work and energy?
Ans: The standard units of measurement for work and energy are the same i.e, Joule (J). As work can be written as a product of force and displacement, so we can also write the unit of work as Newton metre.
What is the difference between force and energy?
Ans: A force is any activity that tends to change a body's condition of rest or motion. Energy is a system attribute that measures a system's ability to accomplish work, for example potential and kinetic energy.
While catching a cricket ball of mass 100 g moving with a velocity of 10 m/s. find the work done in catching the ball.
Ans: Given:
The mass of the ball, $m$ = 100g = 0.1 kg
Initial velocity of the ball, $v_i$ = 10 m/s
Final velocity of the ball, $v_f$ = 0………(As ball get stopped after catching it)
Now applying the concept of work energy principle,
$W=\dfrac{1}{2}mv^2_f-\dfrac{1}{2}mv^2_i$
After putting the values of the quantities, we get:
$W=\dfrac{1}{2}\times (0.1) (0)^2-\dfrac{1}{2}\times (0.1) (10)^2$
$W= 0- 5=-5J$
Hence, the amount of work done in catching a ball is -5J.
Fun Facts
Everything around us is controlled by some kind of force, for example, the revolution of Earth around the Sun and Moon around the Earth is done in a proper orbit because of the presence of gravitational force.
You are able to write on paper because of the presence of frictional force.
Summary
In this post, we have mentioned various concepts like work, force and its types, energy and its types and also about the concept of power. We have discussed the concept of work energy principle and also solved numericals on work energy theorem.
Learning By Doing
At the railway station, you have noticed the coolie is putting up the luggage on his head. In that case, think about whether the work is done or not. If not then why?
FAQs on Understanding the Concept of Force, Work and Energy
1. What is force and what is its standard unit of measurement?
A force is a push or pull upon an object resulting from its interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. The standard SI unit of force is the Newton (N).
2. What is meant by 'work' in the context of physics?
In physics, work is defined as the energy transferred to or from an object when a force acts upon it, causing displacement. For work to be done, the force must cause the object to move in the direction of the force. The SI unit for work is the Joule (J).
3. Why is no work done when you push a stationary wall, no matter how hard you push?
Although you exert a significant force on the wall, no work is done because there is zero displacement. The scientific definition of work requires both a force and a distance moved in the direction of that force (Work = Force × Displacement). Since the wall does not move, the displacement is zero, and therefore, the work done is also zero.
4. What is energy, and what is the main difference between kinetic and potential energy?
Energy is the capacity or ability to do work. The two primary forms of mechanical energy are:
- Kinetic Energy: This is the energy an object possesses due to its motion. For example, a moving cricket ball has kinetic energy.
- Potential Energy: This is the stored energy an object has because of its position or state. For instance, water stored behind a dam has gravitational potential energy.
5. How does the Law of Conservation of Energy apply to a simple swinging pendulum?
The Law of Conservation of Energy states that energy only changes forms; it is never created or destroyed. For a swinging pendulum:
- At its highest point, the pendulum stops momentarily, and all its energy is potential energy.
- As it swings downwards, potential energy is converted into kinetic energy, which is maximum at the lowest point of the swing.
- As it swings up the other side, kinetic energy is converted back into potential energy.
This continuous conversion demonstrates the conservation of energy in a closed system.
6. What is the fundamental relationship between work and energy?
The relationship between work and energy is described by the Work-Energy Theorem. This principle states that the net work done on an object is equal to the change in its kinetic energy. Essentially, doing work on an object is the process of transferring energy to it. If you do positive work, you increase its energy; if you do negative work, you decrease its energy.
7. How is power different from energy?
While often used interchangeably, power and energy are different concepts. Energy is the ability to do work, measured in Joules. Power is the rate at which work is done or energy is transferred. It tells you how fast the energy is being used. The SI unit of power is the Watt (W), where 1 Watt equals 1 Joule per second.
8. Can work be negative, and what is a real-world example?
Yes, work can be negative. Negative work occurs when the force applied on an object is in the opposite direction to its displacement. A clear example is the force of friction. When a box slides across a floor, it moves forward, but the force of friction acts backward. This frictional force does negative work, which removes kinetic energy from the box and causes it to slow down.
