• Energy is a scalar quantity.
• It was first hypothesized by Newton to express kinetic and potential energies.
• We cannot observe energy directly, but we can measure it using indirect methods and analyze its value.
• Energy may be in different forms, such as potential, kinetic, magnetic or electrical.
Potential energy of a system is by virtue of its location with respect to gravitational field. If an object has a mass m, located at elevation h, and acceleration due to gravity is g, then the potential energy is, EPE = mgh (1.1)
Kinetic energy of an object is due to its velocity. If an object is moving with a velocity u, and it has mass m, then its kinetic energy is, …show more content…
If the magnitude of all other energy forms are small in comparison with the kinetic, potential and internal energies, then ETOTAL = EKE + EPE + Ei (1.4)
A small object of mass m=234g slides along a track with elevated ends and a central flat part. The flat part has a length L=2.16m. The curved portions the tracks are frictionless; but it travelling the flat part, the object loses 688 mJ of mechanical energy, due to friction. The object is released at point A, which is height h= 1.05 m above the flat part of the track. Where does the object finally come to rest?
The potential energy U is defined as:
Here, m is the mass of the body, g is the free fall acceleration and h is the fall of height.
To find the potential energy of the object at the point A, substitute 234g for mass of the object m, 9.81 m/s2 for free fall acceleration g and 1.05 m for height h in the equation