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Work Power Energy JEE L1 [What Is Work and Power? Finding Work By Force] | JEE Physics | JEE 2023

Vedantu JEE English・63 minutes read

Understanding work, power, and energy is crucial in physics, with work defined as the product of force and displacement, influenced by the angle between them. The rate of doing work is power, measured in watts, with positive, negative, or zero power indicating energy transfer, taken, or no transfer, respectively.

Insights

Work in physics is defined as the transfer of energy between systems, calculated as the product of force and displacement in the direction of motion, with only forces parallel to displacement contributing to work.
Work done by a force can be positive, zero, or negative based on the angle between force and displacement, where positive work signifies energy input, negative work implies energy extraction, and zero work occurs when force and displacement are perpendicular.
Power, the rate of work done, is calculated as force multiplied by velocity and measured in watts, with positive power indicating energy input, negative power representing energy extraction, and zero power signifying no energy transfer.

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Recent questions

What is work in physics?
Work is the transfer of energy between systems.
How is power calculated?
Power is calculated as force dot velocity.
What is the relationship between power and velocity?
The force required to tow a car at a constant velocity is directly proportional to the velocity itself.
What are the different package options for micro courses?
Three package options: Light, Classic, and Plus versions.
How is work done by a force calculated?
Work done by a force displacing a particle is calculated using integration.

Related videos

Summary

00:00

"Physics: Work, Power, Energy for 11th Grade"

Introduction to the session on work, power, and energy for 11th standard students at Vidantu.
The importance of understanding work, the role of force, and calculating work done by a force.
The speaker's background in teaching physics and the commencement of a long-term batch for 11th standard students.
Schedule of upcoming sessions, with the first session focusing on work for energy.
Encouragement to subscribe to not miss classes and recommendations for seniors or relatives.
Updates available on the Telegram channel for regular information.
Explanation of work as the transfer of energy between systems using the analogy of two Pandus and a bank.
Definition of work in physics as the product of force in the direction of displacement.
Clarification that only forces in the direction of displacement contribute to work.
Explanation of how forces perpendicular to displacement do not contribute to work, using examples like gravity and normal force.

15:13

Work and Energy: Understanding Force and Displacement

One meter is equal to one joule, the SI unit, or one dyne into one centimeter, the CGS unit.
Work is defined as F dot S, where F is force, S is displacement, and theta is the angle between them.
The unit of work is the joule, with 1 joule being 10 to the power of 7 ergs in the CGS unit.
Work is a scalar quantity and does not have a direction; it can be positive, zero, or negative based on the angle between force and displacement.
For acute angles, work is positive; for 90 degrees, it is zero; and for obtuse angles, it is negative.
Work done can be positive when force and displacement are in the same direction, and negative when they are opposite.
Force of 50 newtons acting on a body displacing it by 30 meters at an angle of 120 degrees results in -750 joules of work.
Work done by gravity on a 100-gram mass falling 125 meters for 5 seconds is 125 joules.
Tension of 70 newtons and weight of 50 newtons accelerating a mass upwards at 4 m/s^2 for 2 seconds results in 20 joules of work done by tension.

30:28

Work and Displacement: Forces and Energy Transfers

Displacement is in the direction of cos 0, with a tension of 70 and a displacement of 8, resulting in 560 joules of work done by tension.
Work done by gravity, with a force of 50 and displacement of 8, at an angle of 180 degrees, equals -400 joules.
Total work is the sum of work done by tension and gravity, resulting in 160 joules.
Tension is the pulling force in a thread, acting away, and becomes slack if zero.
Work done by friction on a person walking is zero due to static friction when the foot is at rest.
Friction does not move the person's foot, hence the displacement of friction is zero, leading to zero work done by friction.
Work done by a variable force involves dividing the motion into small steps and integrating force with displacement.
Integration in graphs represents the area under the force versus displacement graph, determining the total work done.
The sign of work done can be positive or negative based on the position of the force graph relative to the displacement axis.
The total work done is the sum of positive and negative areas under the force versus displacement graph, accounting for the direction of the force.

46:57

Understanding Integration: Area Under Graphs and Steepness

Integral does not mean area under the slope; it refers to the area under a graph, while slope is the steepness represented by dy/dx.
Slope is the concept of steepness, represented by dy/dx, which is the same as the slope.
Area under force versus displacement graph gives work, not area under the slope.
When a physical quantity, like P, is integral, it means the area under the graph of that quantity versus time gives the integral value.
Integration involves the height becoming the vertical line, with dt on the horizontal line, and the area giving the integral's value.
Slope represents steepness, not area, and it's incorrect to say area under the slope.
Work done by a force displacing a particle from 4 to -2 meters is calculated using integration of -6x^3 dx from 4 to -2, resulting in 360 joules.
The formula for the area of a trapezium is used to find the work done, which is the area under the force versus displacement graph.
Power is the rate of doing work, calculated as force dot velocity, or force times displacement rate.
One watt of power is one joule of work done in one second, indicating the rate at which work is done.

01:01:40

Power and Derivatives in Physics

The derivative of f dot d s f is a constant when brought outside, following the rules of derivatives.
The derivative of ds by dt is velocity.
One horsepower is equivalent to 746 watts, an important conversion to remember.
Positive power signifies energy given to the system, with force and velocity in the same direction.
Negative power indicates energy taken from the system, with force and velocity opposing each other.
Zero power occurs when force and velocity are perpendicular, resulting in no energy transfer.
Different forces acting on a body can have varying effects on power, such as positive, negative, or zero power.
The force required to tow a car at a constant velocity is directly proportional to the velocity itself.
When the velocity changes four times, the power required increases by 16 times.
The power of the engine required to move a train at a given speed is determined by the velocity and frictional force acting on it.

01:16:17

"Micro courses for 11th and 12th standard"

Micro courses available for 11th and 12th standard in English and Hindi, including parent-teacher sessions, guidance, and strategy sessions.
Three package options: Light, Classic, and Plus versions, with live and recorded classes, tests, assignments, and the exclusive Tatwa module booklet.
Course starting this Monday at a reasonable price of 3600 rupees per month, with a 10% discount using the coupon code SHPRO, and exclusive micro courses only accessible through the Pro subscription.

Try it yourself — It’s free.