Consider a tennis ball placed on a table. Now imagine that you are also holding another tennis ball (same weight and size) in your hand. Since both tennis balls are stationary and neither has any kinetic energy. Next let the ball loose from your hand and it will start moving in the direction of gravity. As the ball hits the ground, it has a certain velocity value. The velocity of the ball dropped on the floor depends on the height it is dropped from. In Physics energy must be conserved and since no additional energy was added the scientists propose that the ball had a potential energy which was converted to kinetic energy. Similarly, the ball placed on the table also has potential energy even though it is not moving at all.
Physicists across the world use Newton’s law of motion to calculate the motion of an object. According to the Newton’s law energy must be conserved. Therefore the ball on the table must have some energy which allows it move in the direction of gravity. This energy of a stationery object is known as the potential energy. Calculation of motion of a dropped ball is also fairly simple. Kinetic energy at the bottom must be equal to the potential energy at the top. Therefore, if h is the height the ball is dropped from and g is the gravity then the speed of the ball can be calculated using the formula given below
Sqrt (2 x h x g)
Although the theory of kinetic energy and potential energy is a strange, it can help us solve a variety of engineering problems. The term electric potential energy is also derived from this concept. By knowing the forces exerted electric charges, it is possible to calculate the motion of an object in an electric field.