Question

When an object falls freely towards the earth, then its total energy:

• A. Increases
• B. Decreases
• C. Remains constant
• D. First increases and then decreases

Hint:

In real-world conditions, air resistance causes some energy to be converted into heat, which is why total mechanical energy slightly decreases over time.

Answer 1

The Correct Option is C

Step 1: The big idea.
Energy is never lost. It only changes from one form to another. This is the law of conservation of energy.

Step 2: Two kinds of energy here.
An object high up has potential energy. A moving object has kinetic energy.

Step 3: As the object falls.
Its height drops, so its potential energy goes down. We can write \[ PE = mgh \] so less height means less potential energy.

Step 4: At the same time.
The object speeds up, so its kinetic energy goes up. We can write \[ KE = \frac{1}{2}mv^2 \] so more speed means more kinetic energy.

Step 5: The balance.
If we ignore air friction, the potential energy lost is exactly equal to the kinetic energy gained. So the two changes cancel out.

Step 6: Conclusion.
The total energy, which is potential plus kinetic, stays the same all through the fall.
Answer: Remains constant