# Why is Work Calculated as Fdcosθ Even with Gravity?

• vivekfan
In summary, work in physics is defined as the product of force and displacement in the direction of the force. It is closely related to energy, as it is a measure of energy transfer. Work can be negative when the force applied is in the opposite direction of the displacement. The unit of measurement for work is joules (J) and the direction of work is determined by the direction of the force and displacement.
vivekfan

## Homework Statement

This is conceptual question...Is work a scalar or vector quantity? Is it force times distance or displacement?

And it just Fdcostheta by definition of the dot product. Why is it cos theta even when you calculate work done by gravity?

Fdcos theta

## The Attempt at a Solution

Just need conceptual clarification.

hello,

just check http://en.wikipedia.org/wiki/Mechanical_work"

I suppose,it helps.

Dot product of two vectors is scalar

Last edited by a moderator:

Work is a scalar quantity, meaning it only has magnitude and no direction. It is calculated by multiplying the magnitude of the force applied in the direction of motion by the displacement of the object.

When calculating work done by gravity, the force and displacement are in the same direction, so the cosine of the angle between them is 1. This results in the simplified equation of W = Fd. However, when the force and displacement are not in the same direction, the cosine of the angle between them must be considered in order to accurately calculate the work done. This is why the equation becomes W = Fdcos theta. The cosine term takes into account the component of the force that is actually contributing to the displacement of the object.

## 1. What is the definition of work in physics?

In physics, work is defined as the product of force and displacement in the direction of the force. It is a measure of energy transfer that occurs when a force is applied over a distance.

## 2. How is work related to energy?

Work and energy are closely related concepts in physics. Work is the transfer of energy from one object to another, or from one form to another. The work done on an object is equal to the change in its energy.

## 3. Can work be negative?

Yes, work can be negative. This occurs when the force applied is in the opposite direction of the displacement. In this case, work is considered to be done against the force, resulting in a decrease in energy.

## 4. What is the unit of measurement for work?

The unit of measurement for work is joules (J) in the International System of Units (SI). This is equivalent to a force of one newton (N) applied over a distance of one meter (m).

## 5. How is the direction of work determined?

The direction of work is determined by the direction of the force and the displacement. If the force and displacement are in the same direction, then the work is considered positive. If they are in opposite directions, then the work is considered negative.

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