The law of conservation of energy states that energy can neither be created nor destroyed, but it can be converted from one form to another.
The total energy of an isolated system remains constant. Although energy changes its form, the total amount of energy before and after the change remains the same.
Mechanical energy is the sum of kinetic energy and potential energy.
Total Mechanical Energy = KE + PE
At height h:
PE = m g h , KE = 0
At ground level:
PE = 0 , KE = (1/2) m v2
Thus, total energy remains constant.
Q1. The law of conservation of energy states that energy: A) Can be created B) Can be destroyed C) Can neither be created nor destroyed D) Always remains kinetic Answer: C Q2. Total mechanical energy is the sum of: A) Force and power B) Work and power C) Kinetic and potential energy D) Heat and light energy Answer: C Q3. During free fall of a body, which energy conversion takes place? A) KE to PE B) PE to KE C) Heat to KE D) Electrical to KE Answer: B Q4. Law of conservation of energy is valid when: A) External force acts B) Friction is very high C) No external force acts D) Mass changes Answer: C Q5. At the highest point of motion of a freely falling body, its: A) KE is maximum B) PE is zero C) KE is zero D) Total energy is zero Answer: C Q6. Which of the following follows conservation of energy? A) Motion with friction B) Isolated system C) Open system D) System with energy loss Answer: B Q7. In a pendulum, energy continuously changes between: A) Heat and sound B) KE and PE C) Chemical and electrical D) Light and heat Answer: B Q8. Which statement is correct? A) Energy can be destroyed B) Energy can be created C) Energy only changes form D) Energy always remains constant in one form Answer: C
Energy can neither be created nor destroyed, but it can be converted from one form to another.
Mechanical energy = Kinetic energy + Potential energy
MCQs and numericals are asked on energy conversion and conservation of mechanical energy.
