Conservation of Mechanical Energy – Class 11 | Chapter – 6 | Physics Short Notes Series PDF for NEET & JEE

Conservation of Mechanical Energy: Conservation of mechanical energy is a fundamental principle in physics that states that the total mechanical energy of an isolated system remains constant if there are no external forces acting on it. Mechanical energy is the sum of an object’s potential energy and kinetic energy.

Conservation of Mechanical Energy

The principle of conservation of mechanical energy can be expressed mathematically as:

Emechanical = PE + KE = constant

Where,

• Emechanical is the total mechanical energy of the system
• PE is the potential energy of the system
• KE is the kinetic energy of the system.

This principle can be applied to a variety of physical systems, including those involving gravity, springs, and pendulums. For example, consider a ball of mass m that is dropped from a height h above the ground. As the ball falls, its potential energy decreases while its kinetic energy increases. However, the total mechanical energy of the system (ball + Earth) remains constant, as there are no external forces acting on it. At the moment the ball hits the ground, all of its potential energy has been converted to kinetic energy, resulting in a maximum speed of v = √(2gh).

Applications of Conservation of Mechanical Energy

The principle of conservation of mechanical energy is a fundamental concept in physics that has many practical applications. Here are some examples:

• Roller Coasters: Roller coasters rely on the conservation of mechanical energy to operate. At the top of the first hill, the coaster car has the highest potential energy, which is converted to kinetic energy as the car travels down the hill. As the car goes up the next hill, its kinetic energy is converted back to potential energy, which is then used to propel the car through the rest of the ride.
• Pendulum clocks: Pendulum clocks use the conservation of mechanical energy to keep time. The pendulum swings back and forth, with the potential energy being converted to kinetic energy and back again. By adjusting the length of the pendulum, clockmakers can ensure that the period of the pendulum (the time it takes to complete one swing) remains constant, resulting in accurate timekeeping.
• Bungee jumping: Bungee jumping is a popular activity that relies on the conservation of mechanical energy. As the jumper falls, their potential energy is converted to kinetic energy. When the bungee cord stretches and begins to recoil, some of the kinetic energy is converted back to potential energy, causing the jumper to bounce back up.
• Electric generators: Electric generators convert mechanical energy into electrical energy. The mechanical energy is usually generated by steam turbines or hydroelectric turbines, which convert the potential energy of water or steam into mechanical energy. This mechanical energy is then used to rotate a coil of wire in a magnetic field, generating an electric current.
• Baseball pitching: Baseball pitchers use the conservation of mechanical energy to throw the ball with maximum speed. By transferring energy from their legs to their arms, pitchers can generate greater kinetic energy in the ball, resulting in a faster pitch.

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