Potential Energy — IISER Physics MCQs with Solutions
Free IISER Physics Potential Energy MCQs with step-by-step solutions (8 questions). Part of Work, Power and Energy. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Potential Energy · easy · theory
Potential energy can be defined only for:
A. Conservative forces ✓ Correct
B. Contact forces only
C. All forces including friction
D. Constant forces only
Solution: U is defined through ΔU = −W_cons, which requires path-independent (conservative) forces. Its zero level is an arbitrary choice.
Q2 — Potential Energy · medium · theory
A spring is compressed by x, and separately stretched by the same x. The elastic potential energies stored are:
A. Greater for the stretch
B. Greater for the compression
C. Equal (½kx² in both cases) ✓ Correct
D. Zero for compression
Solution: U = ½kx² depends on x², so equal deformation stores equal energy either way.
Q3 — Potential Energy · easy · numerical
A 2 kg block is raised through a height of 15 m. The gain in its potential energy is:
A. 300 J ✓ Correct
B. 150 J
C. 30 J
D. 600 J
Solution: ΔU = mgh = 2×10×15 = 300 J.
Q4 — Potential Energy · medium · numerical
A spring of k = 100 N/m is stretched by 20 cm. The potential energy stored is:
A. 4 J
B. 2 J ✓ Correct
C. 0.2 J
D. 20 J
Solution: U = ½kx² = ½×100×(0.2)² = 50×0.04 = 2 J. Trap: convert cm to m before squaring.
Q5 — Potential Energy · hard · numerical
A uniform rod of mass 2 kg and length 1 m lies flat on the ground. The work needed to stand it vertically on one end is:
A. 5 J
B. 40 J
C. 20 J
D. 10 J ✓ Correct
Solution: Only the centre of mass matters: it rises by L/2 = 0.5 m. W = mg(L/2) = 2×10×0.5 = 10 J.
Q6 — Potential Energy · medium · numerical
A spring stores 4 J of energy when stretched by x. Keeping the same spring, the energy stored at stretch 2x is:
A. 4 J
B. 12 J
C. 8 J
D. 16 J ✓ Correct
Solution: U ∝ x² ⇒ ×4 at double stretch: 16 J.
Q7 — Potential Energy · hard · theory
Which statement about potential energy is correct?
A. It is always positive
B. It can be negative — e.g. a bound satellite–Earth system ✓ Correct
C. It is frame-independent but always positive
D. It is defined for frictional forces too
Solution: With the zero chosen at infinity, gravitationally bound systems have U < 0. Only the CHANGE in U is physical; the reference is arbitrary.
Q8 — Potential Energy · hard · numerical
A pendulum bob of mass 0.5 kg on a string of length 2 m is pulled aside until the string makes 60° with the vertical. The gain in potential energy of the bob is:
A. 10 J
B. 8.7 J
C. 2.5 J
D. 5 J ✓ Correct
Solution: Rise h = L(1 − cos60°) = 2 × 0.5 = 1 m. ΔU = mgh = 0.5×10×1 = 5 J. Trap: h is L(1 − cosθ), not L sinθ.