Question

What is mechanical energy? How does it differ from thermal energy? What are the forms of mechanical energy of a fluid stream?

Short answer

Answer: Mechanical energy is the energy possessed by an object due to its motion (kinetic energy) and its position (potential energy). It is different from thermal energy, which is associated with the microscopic properties of an object, related to the random motion of its molecules. The three main forms of mechanical energy in a fluid stream are kinetic energy, potential energy, and internal energy. Kinetic energy is related to the motion of fluid particles, potential energy is related to the position of fluid particles in a gravitational field, and internal energy is associated with the internal forces within the fluid, such as pressure.

Step-by-step solution

Definition of Mechanical Energy

Mechanical energy is the energy possessed by an object due to its motion (kinetic energy) and its position (potential energy). It is the sum of kinetic and potential energy at a given point in time.

Mechanical Energy vs. Thermal Energy

Mechanical energy is associated with the macroscopic properties (large scale) of an object, such as its position and velocity. Thermal energy, on the other hand, is associated with the microscopic properties (small scale) of an object, related to the random motion of its molecules. In other words, mechanical energy is the energy of organized motion, while thermal energy is the energy of disorganized motion.

Forms of Mechanical Energy in a Fluid Stream

There are three main forms of mechanical energy in a fluid stream: 1. Kinetic Energy: This is the energy associated with the motion of the fluid particles. It depends on the mass and velocity of the fluid particles. Mathematically, kinetic energy (KE) can be represented as KE = \frac{1}{2}mv^2, where m is the mass of the fluid particles and v is their velocity. 2. Potential Energy: This is the energy possessed by the fluid particles due to their position in a gravitational field. It depends on the mass of the fluid particles, the gravitational acceleration, and the height of the particles above a reference level. Mathematically, potential energy (PE) can be represented as PE = mgh, where m is the mass of the fluid particles, g is the gravitational acceleration, and h is the height above the reference level. 3. Internal Energy: This is the energy associated with the internal forces within the fluid, such as pressure. In a fluid stream, the internal energy is related to the work done to compress or expand the fluid and is represented by the product of pressure (P) and the volume (V) of the fluid.