Lesson 18: Summary on Work, Energy and Power
- Energy Types and Characteristics Energy can be classified mainly into kinetic and potential energy.
- Kinetic energy is associated with the motion of objects, while potential energy is related to the position or shape of an object.
- Energy plays a crucial role in physics as it is the capacity to do work.
- It exists in various forms and can be transformed from one type to another, but the total amount of energy remains constant in a closed system.
- This principle is known as the conservation of energy, which states that energy cannot be created or destroyed.
- Work and its Implications Work is a means of transferring energy from one body to another or transforming energy from one form to another.
- In physics, work is defined as the product of the force applied to an object and the displacement in the direction of the force.
- Work can be positive, negative, or zero depending on the direction of the force relative to the displacement.
- For instance, when lifting an object, chemical energy from muscles is converted into potential energy of the object.
- The SI unit of work is the joule (J).
- Conservative and Non-Conservative Forces Forces are categorized into conservative and non-conservative types.
- Conservative forces, such as gravitational force, do work that is independent of the path taken and can be completely recovered.
- Non-conservative forces, like friction, depend on the path and cause a change in the mechanical energy of a system.
- The work done by non-conservative forces results in the dissipation of energy, often as heat, and cannot be fully recovered.
- Kinetic and Potential Energy in Action Kinetic energy (KE) is given by the formula KE = ½ mv², where m is mass and v is velocity.
- It is a scalar quantity and is associated with the motion of an object. Potential energy (PE) is the energy stored in an object due to its position or shape.
- Gravitational potential energy, for example, is PE = mgh, where m is mass, g is gravitational acceleration, and h is height.
- Elastic potential energy, stored in stretched or compressed springs, is PE = ½ kx², where k is the spring constant and x is the displacement from equilibrium.
- Power and Work-Energy Theorem Power is the rate of doing work or converting energy, measured in watts (W).
- It quantifies how quickly work is done or energy is transferred.
- The work-energy theorem links work done to changes in kinetic energy, stating that the net work done by forces on an object equals the change in its kinetic energy.
- This theorem is fundamental in understanding energy transformations in mechanical systems.
- Power is defined as the rate of doing work in the minimum possible time.
- It is the amount of work or energy that is transferred per unit of time.
- Power is directly proportional to energy and work done. The more work done or energy consumed, the more will be power.
- Power is directly proportional to work and is inversely proportional to time.
- Power is also used to calculate the efficiency of the device. The formula is
- Efficiency= output power/ input power
- The SI unit of power is Watt.