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JEE Main Work, Energy and Power Revision Notes

## JEE Main Work, Energy and Power Revision Notes - PDF Download

When a constant force F is applied on the box upon the smooth surface, at a certain point of application, it offers a displacement s.

Mathematically, it can express as W = F s cos Θ

(Image to be added soon)

Here,

Θ = the angle between F and s (displayed in the above image)

Here, F cos Θ plays an important role in the work done.

### Role of Gravity in Work Done

The work done by gravity is said to be negative if an object is moving in an upward direction. The expression for the statement is,

Wg = - m.g.h

Note: Work done is positive when it is falling from certain heights.

### Role of Friction in Work Done

A concept is always there in our mind that the force of friction results in a negative work. However, as per the observation, it is concluded that the work done by friction may be zero, positive, negative or zero according to the condition.

### Role of a Variable Force in Work Done

If there is a chance of any alteration or variation of magnitude and direction of a force in a three-dimensional space, the expression can be obtained as a function of the position vector F.

Consider that a force is present in 3 – D space. Also, assume that the force’s magnitude as well as direction changes for some reason.

The coordinates are (x, y, z) for this force F.

We can write the work done formula as

\[\overrightarrow{F}\] . \[\overrightarrow{ds}\] = dW

### Work Power and Energy JEE Notes

The notes on the work power and energy are given below.

### Work-Energy Theorem

The basic theorem for work, power and energy can be defined as the difference between two kinetic energies obtained by a single object by the change of force.

It can be written as,

W = Kf – Ki = ΔK

### Power

The definition of Power can be explained below:

Power has different types of physical forms. If we plot the concept correctly, power can be illustrated as the rate of doing work.

Otherwise, it can be inferred that it is the net energy consumed per unit time.

P = W / t

### Energy

Energy can be depicted as the ability to do some work. According to the observations, we can’t destroy or create energy, rather it is the transformation from one form to another. We use ‘Joules’ as the measurement of energy.

Mainly, energy is found in two forms, such as potential energy (P.E.) and kinetic energy (K.E.).

Kinetic Energy is recognized as the energy in motion.

Potential Energy is recognized as the energy kept in an object.

P.E. = m.g.h

K.E. = 1 / 2 (m.v2)

### Solved Work Power and Energy Examples

Q1. If we drag an object upon a horizontal surface by applying 200 N force acting parallel to the surface, then what will be the work done by the force for moving the object up to 9 meters?

Ans: According to the question,

Force, F = 200 N

Distance, d = 9 m

Here, F and d both are acting in the same direction.

And, θ = 00

θ = the angle of the force to the direction of movement

Work done formula, W = F Cos θ

= 200 x 9 x Cos 0 [We know, Cos 00 = 1]

= 1800 J

Q2. A 1500 kg of mass of a truck is lifted by the garage hoist up to 3 meters above the ground in 25 seconds. What will be the power applied upon the truck?

Ans: We need to calculate in a systematic order so that it will be easy for us to obtain the power.

Force = mg = 1500 x 9.81 = 14715 N.

Work done = F * d = 9810 N x 5 m = 19620 Nm = 73575 J.

Power (P) = W / t = 73575 J / 25 s = 2943 J / s

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There are some features about work power and energy chapter that can surely change your mind to choose Vedantu:

The article is well organized and helpful to learn with ease.

This chapter’s notes are prepared by specialists, which can help the students a lot.

The practice of model papers of this chapter can give you the ability to score more in the JEE as well as NEET exams.

### Work Power and Energy PYQP

PYQP is recognized as the previous year’s question papers. Students can access the PYQP by log in to our website. There some points are given below; I would like to recommend to our students;

The PDF also contains numerical problems that are solved precisely by explaining each question.

Answers are presented for the respective questions in the pdf as per the JEE syllabus.

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1. Why is the Force of Gravity Negative?

It has been proven that acceleration due to gravity is always negative. When an object is in its free-falling state, it has been affected only by gravity, which is - 9.81 m/s2 irrespective of the direction.

2. is the Delivered Power Negative?

According to the research, the total power transported to a circuit is equal to the total power absorbed. It has been proven that the power delivered is a negative quantity and power absorbed is a positive quantity

If we deeply study the laws of conservation of mass, it suggests that the total power of all elements in a circuit results in zero.

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