NEET Physics: Kinetic and potential energies Practice Questions

Correct answer: B — Mass and height

Gravitational potential energy (P) is calculated as mgh, where m is mass, g is acceleration due to gravity, and h is the height.

Correct answer: D — Velocity squared

Kinetic energy is KE = 1/2 mv². Therefore, kinetic energy is directly proportional to the square of the velocity (v²), assuming mass (m) is constant.

Correct answer: C — It is maximum

As the ball falls, potential energy is converted entirely into kinetic energy. At the ground, it has maximum kinetic energy, assuming no energy loss.

Correct answer: B — 25 J

Kinetic energy (K) is calculated using the formula K = 1/2mv². Substituting the values: K = 1/2 (2 kg) (5 m/s)² = 1 × 25 = 25 J.

Correct answer: A — Zero

Potential energy is defined relative to a reference point. If the object is held at a constant height, the change in height (Δh) is zero, thus the change in potential energy is zero (if the reference point is set there).

Correct answer: B — It doubles

Gravitational Potential Energy is given by U = mgh. If the height (h) is increased while mass (m) and gravity (g) are constant, the potential energy (U) increases proportionally to the height.

Correct answer: B — The sum of kinetic energy and potential energy remains constant

In simple harmonic motion, the total mechanical energy (KE + PE) is conserved. The energy continuously converts between kinetic energy (related to motion) and potential energy (related to position).

Correct answer: B — K_A is four times K_B

Since K ∝ v², if v_A = 2v_B, then K_A = 1/2m(2v_B)² = 1/2m(4v_B²) = 4 (1/2mv_B²) = 4K_B.

Correct answer: B — 150 J

Total mechanical energy is the sum of kinetic energy and potential energy. Total Energy = KE + PE = 50 J + 100 J = 150 J.

Correct answer: D — Four times

Since K = 1/2mv², if v is doubled to 2v, the new kinetic energy becomes 1/2m(2v)² = 4(1/2mv²), which is four times the original energy.

Correct answer: A — The sum of KE and PE is constant (Conservation of Energy)

In any system where only conservative forces are involved, the total mechanical energy (E = K + U) is conserved. This means the sum of kinetic energy and potential energy remains constant throughout the motion.

Correct answer: D — Constant

In the absence of non-conservative forces (like friction), the total mechanical energy (K + P) remains constant throughout the motion.

Correct answer: B — Zero

Kinetic energy is given by K = 1/2mv². If the velocity (v) is zero, then K = 1/2m(0)² = 0. This occurs at the extreme points of simple harmonic motion.

Correct answer: A — Zero

Mechanical energy is the sum of kinetic energy (K = 1/2 mv²) and potential energy (U = mgh). If the velocity is constant, the kinetic energy remains constant. Since the gravitational potential energy changes with height, the rate of change of total mechanical energy is zero only if the force doing work is zero, or if the rate of change of U exactly balances the rate of change of K. Here, since the object is moving at constant velocity, the net force is zero (or gravity is balanced by another force), thus dE/dt=0.

Correct answer: C — It increases

The total mechanical energy of the pendulum is determined by the initial release conditions (amplitude and initial position). Increasing the amplitude means the mass moves farther, thus storing more potential energy, leading to an increase in the total mechanical energy.