Life is impossible without energy. The Sun is the biggest natural source of energy to us. Many of our energy sources are derived from the Sun. An object having a capability to do work is said to possess energy. The object which does the work loses energy and the object on which the work is done gains energy.
In this article, I will take you through some important revision notes over Potential Energy and Kinetic Energy from the Chapter 11 of CBSE Science Class 9, WORK AND ENERGY.
NOTES:
- There are various forms of energy, including mechanical energy (kinetic energy + potential energy), heat energy, light energy, chemical energy, and electrical energy.
- The unit of energy and work is joule, after an outstanding British physicist named James Prescott Joule (1818-1889).
- Kinetic energy is the energy possessed by an object due to its motion. The kinetic energy of an object increases with its speed.
- The kinetic energy possessed by an object of mass, m and moving with a uniform velocity, v is-
- The potential energy possessed by the object is the energy present in it by virtue of its position or configuration.
- An object increases energy when raised through a height. This is because work is done on it against gravity while it is being raised. The energy present in such an object is the gravitational potential energy.
- Since, work done on the object is equal to mgh, an energy equal to mgh units is gained by the object. This is the potential energy of the object-
(Ep) = mgh
4. It is useful to note that the work done by gravity depends on the difference in vertical heights of the initial and final positions of the object and not on the path along which the object is moved.
