Define the work done by a force.

The work done by a force is the amount of energy transferred when an object is moved by that force.

In physics, work is a measure of energy transfer that occurs when an object is moved. It is calculated by multiplying the force applied to the object by the distance over which the force is applied, and the cosine of the angle between the force and the direction of motion. This is represented by the formula W = Fd cos θ, where W is work, F is force, d is distance, and θ is the angle between the force and the direction of motion.

Work is measured in joules (J) in the International System of Units (SI). One joule is equivalent to one newton of force causing a one metre displacement. Therefore, the work done by a force of 1 newton in moving an object 1 metre in the direction of the force is 1 joule.

It's important to note that work is only done when the force and the displacement are in the same direction. If the force is perpendicular to the direction of motion, no work is done. This is because the cosine of 90 degrees is zero, making the work done zero as well.

Furthermore, work can be either positive or negative. When the angle between the force and the direction of motion is less than 90 degrees, the work done is positive, indicating that the force is doing work on the object. Conversely, when the angle is greater than 90 degrees, the work done is negative, indicating that the object is doing work against the force.

In summary, the concept of work in physics is a way of quantifying the energy transfer that occurs when a force acts on an object to cause a displacement. It is a scalar quantity, meaning it only has magnitude and no direction, and it is dependent on both the force applied and the distance over which it is applied.