(i) Name two forms of mechanical energy. Define the SI unit of energy.
(ii) A man of mass 50 kg jumps from a height of 0.5 m. If g = 10 ms, what will be his energy at the highest point?
(iii) Calculate the energy of a body of mass 20 kg moving with velocity of 0.1 m.
(i) Two forms of mechanical energy are
(a) Kinetic energy and
(b) Potential energy (1)
The SI unit of energy is joule (J). 1J is the amount of work done on an object when a force of IN displaces it by 1 m along the line of action of force.
(ii) Given, m = 50 kg,
h = 0.5 m, g= 10 ms”2
At highest point, kinetic energy is converted into potential energy. "
.-. PE = mgh = 50 x 10 x 0.5 = 250 J
(iii) Given, m = 26 kg, v=0.1 m
As we know that, a moving body has kinetic energy.
KE = 1/2 m ${{v}^{2}}$
= 1/2 x 2 x 0.1 x 0.1 = 0.1 J