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Workdone By Variable Force Formula -Definition, Introduction

Work done by a variable force is a concept in physics that involves calculating the amount of energy transferred when an object is subjected to a force that changes in magnitude or direction as the object moves.
authorImageMurtaza Mushtaq10 Sept, 2023
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Workdone By Variable Force Formula

Workdone by  variable force is a concept in physics that involves calculating the amount of energy transferred when an object is subjected to a force that changes in magnitude or direction as the object moves. To calculate the work done by a variable force, you typically need to use calculus, specifically integration, because the force is not constant over the entire distance the object moves.

The formula for calculating work done by a variable force F(x) over a given distance is given by: Where: - W is the work done (measured in joules, J). - F(x) is the variable force as a function of position \(x\). - dx represents an infinitesimally small displacement along the path of motion. - xf and xi are the initial and final positions, respectively, of the object. Here are the basic steps to calculate the work done by a variable force:
  1. Determine the expression for the force as a function of position, \(F(x)\). This could be given in the problem statement or derived from a physical model.
  2. Identify the initial and final positions of the object, \(x_1\) and \(x_2\).
  3. Set up the integral from \(x_1\) to \(x_2\) with \(F(x)\) as the integrand and \(dx\) as the differential displacement.
  4. Evaluate the definite integral to find the work done.

Also Check - Thermodynamics formula

It's important to note that the direction of the force and the direction of motion should be taken into account when calculating work done. If the force and the displacement are not in the same direction, you may need to use vector dot product notation or break the force into components parallel and perpendicular to the displacement. Also, remember that work done by a force can be positive, negative, or zero, depending on whether the force helps, opposes, or has no effect on the motion of the object. In some cases, when the force varies continuously and is expressed as a mathematical function, you can use integration to calculate the work done precisely. However, if the force varies discretely (e.g., in steps), you can approximate the work done by breaking the motion into smaller segments and calculating the work done in each segment, then summing them up.

Also Check - Work, Energy & Power Formula

Examples Workdone By Variable Force

Here are 10 theoretical examples of calculating work done by variable forces, each with a brief explanation:
  1. Spring Force:
- Explanation: When you compress or extend a spring, the force it exerts is proportional to the displacement from its natural length according to Hooke's Law. Calculate the work done in compressing or extending the spring from one position to another.
  1. Gravitational Force:
- Explanation: When you lift an object against gravity, the force of gravity varies with height. Calculate the work done in lifting an object vertically to a certain height by integrating the gravitational force over the distance.
  1. Frictional Force:
- Explanation: When an object moves on a surface, the frictional force opposing its motion can vary. Calculate the work done in overcoming friction as the object moves from one point to another.

Also Check - Unit, Dimension & Vector Formula

  1. Electric Force:
- Explanation: When a charged particle moves in an electric field with varying strength, the force experienced by the particle varies. Calculate the work done in moving the particle between two points in the field.
  1. Magnetic Force:
- Explanation: When a charged particle moves through a magnetic field with varying intensity, the magnetic force acting on it changes. Calculate the work done in moving the particle along a specified path in the magnetic field.
  1. Tension in a Rope:
- Explanation: When lifting an object using a pulley system, the angle of the rope can change, altering the tension force. Calculate the work done by tension in lifting the object as it moves through its displacement.
  1. Gas Expansion:
- Explanation: In processes like adiabatic or isothermal expansion, the force exerted by a gas inside a container varies as it expands. Calculate the work done by or on the gas as it changes volume.
  1. Variable Wind Resistance:
- Explanation: When a parachute is deployed during freefall, air resistance (drag) varies with altitude due to changes in air density and velocity. Calculate the work done against air resistance as the parachute descends.
  1. Stretching a Rubber Band:
- Explanation: When stretching a rubber band, the force required increases non-linearly as the band stretches. Calculate the work done in stretching the rubber band from one length to another.
  1. Fluid Resistance:
- Explanation: When an object moves through a fluid, such as swimming in water or flying through the air, the resistance force (drag) depends on the object's velocity and shape. Calculate the work done against fluid resistance as the object moves through the fluid. In each case, understanding how the force varies with displacement or position is essential for setting up the integral to calculate the work done. Integration allows you to account for the changing force over the entire displacement and find the total work done.

Workdone By a Variable Force Formula FAQs

What is the definition of work in physics?

In physics, work is the measure of energy transfer that occurs when a force acts on an object and causes it to move a certain distance in the direction of the force.

How is work related to force and displacement?

Work (W) is calculated by multiplying the force (F) applied to an object by the displacement (d) it undergoes in the direction of the force, using the formula: W = F *d

What are the units of work?

The SI unit of work is the joule (J), which is equivalent to one newton-meter (1 N·m). In other systems, work may be expressed in units such as foot-pounds or ergs.

What does negative work mean in physics?

Negative work occurs when the force applied to an object opposes its motion or direction of displacement. It signifies that energy is being taken away from the object's kinetic energy.
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