Practical (SI) unit of work in mechanics Which is the standard practical unit of work used in engineering mechanics?

Introduction / Context:
Units must be clearly distinguished between force, work/energy, and power. In the International System of Units (SI), work and energy share the same unit, used universally in engineering calculations and specifications.

Given Data / Assumptions:

• Work W = Force * Displacement along the line of action.
• Use SI base and derived units.

Concept / Approach:

The SI unit of work is the Joule (J), defined as 1 Newton of force acting over 1 meter of displacement: 1 J = 1 N·m. The Newton (N) is the unit of force, the Watt (W) is power (J/s), and the Dyne and Erg are CGS units.

Step-by-Step Solution:

Verification / Alternative check:

Dimensional analysis confirms [work] equals [energy], reinforcing that Joule is also the unit of energy.

Why Other Options Are Wrong:

Erg and Dyne belong to the CGS system (1 erg = 1 dyne·cm); Newton is force; Watt is power, not work.

Common Pitfalls:

Confusing Newton-meter as torque only; in SI, N·m is the dimension for both torque and work, but work is a scalar energy transfer, while torque is a vector moment.

Final Answer:

Joule