When a body falls freely under gravity, which statement is correct?
A. Total energy is not conserved
B. Kinetic energy decreases
C. Mechanical energy remains constant
D. Potential energy increases
Answer: Option C
Solution (By JKSSB Mock Tests)
In free fall under gravity alone, mechanical energy (kinetic + potential) is conserved, assuming no air resistance. Potential energy decreases while kinetic energy increases, sum constant. Law of conservation of mechanical energy. Non-conservative forces absent.
Explanation:
When equal distances are covered with different speeds v1 and v2, the average speed is not the arithmetic mean, but the harmonic mean of the two speeds. Total distance = 2x. Total time = (x/v1) + (x/v2). Average speed = Total Distance / Total Time = 2x / [x(1/v1 + 1/v2)] = 2v1v2 / (v1 + v2).
Explanation:
The acceleration due to gravity at a depth 'd' is given by g' = g(1 - d/R), where R is the radius of the Earth. If we go to the center of the Earth, the depth 'd' becomes exactly equal to R. Substituting d = R into the formula gives g' = g(1 - R/R) = g(1 - 1) = 0. So, gravity is zero at the core.
No comments yet. Be the first to start the discussion!