Work (physics)

Work (physics)

In physics, work is the measure of energy transfer that occurs when an object is moved by an external force along a displacement. It is a scalar quantity with dimensions of energy, and its SI unit is the joule (J).

Definition

In the case of a constant force, work is the scalar product of the force acting on an object and the displacement caused by that force. Though both force and displacement are vector quantities, work has no direction due to the nature of a scalar product (or dot product) in vector mathematics.

Mathematical calculation

The work, W, done by a constant force of magnitude F on a point that moves a displacement s in the direction of the force is the product:

W = F • s • cos θ

where F is the magnitude of the force, s is the magnitude of the displacement, and cos θ is the cosine of the angle between the direction of the F and the direction of the s.

Work-energy principle

The work-energy principle states that an increase in the kinetic energy of a rigid body is caused by an equal amount of positive work done on the body by the resultant force acting on it.

Units

In the International System of Units (SI), the unit of work is the joule (J), which is defined as the work expended by a force of one newton through a displacement of one metre.

See also

• Energy
• Force
• Displacement (vector)
• Kinetic energy
• Potential energy

References

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