Which of the following is a unit of energy?

The Joule (J) is the correct choice because it is the standard unit of energy in the International System of Units (SI). It measures the amount of energy transferred when a force of one newton is applied over a distance of one meter, or the energy expended in one second when one watt of power is used. This makes the Joule a fundamental unit for quantifying energy in various forms, such as kinetic, potential, thermal, and electrical energy.

On the other hand, Pascal (P) is a unit of pressure, defined as one newton per square meter. Newton (N) is a unit of force, representing the force required to accelerate one kilogram of mass by one meter per second squared. Watt (W) is a unit of power, which quantifies the rate of energy transfer over time, specifically one joule per second. While Pascal, Newton, and Watt are all related to energy and its dynamics, they do not measure energy directly, making Joule the only unit among the choices that specifically represents energy.