Centripetal & Centrifugal Force — IISER Physics MCQs with Solutions
Free IISER Physics Centripetal & Centrifugal Force MCQs with step-by-step solutions (8 questions). Part of Circular Motion. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Centripetal & Centrifugal Force · easy · theory
Centrifugal force is:
A. The force that keeps a body in a circle
B. A real reaction to the centripetal force
C. Always present in the ground frame
D. A pseudo force that appears only in the rotating (non-inertial) frame ✓ Correct
Solution: It exists only for observers in the rotating frame (magnitude mω²r, outward). In the inertial frame only the real centripetal force acts. Trap: it is NOT the Newton's-third-law pair of the centripetal force.
Q2 — Centripetal & Centrifugal Force · medium · theory
A stone whirled on a string breaks free. In the ground frame, immediately afterwards it moves:
A. Radially inward
B. Radially outward
C. In a spiral
D. Along the tangent to the circle at the point of release ✓ Correct
Solution: With no centripetal force, inertia carries it along its instantaneous velocity — the tangent. "Flying outward" is the rotating-frame illusion.
Q3 — Centripetal & Centrifugal Force · easy · numerical
A 0.5 kg stone moves in a horizontal circle of radius 2 m at 6 m/s. The centripetal force is:
A. 3 N
B. 36 N
C. 18 N
D. 9 N ✓ Correct
Solution: F = mv²/r = 0.5×36/2 = 9 N.
Q4 — Centripetal & Centrifugal Force · medium · numerical
A 2 kg body is whirled at 5 rad/s in a circle of radius 0.4 m. In the rotating frame, the centrifugal force experienced is:
A. 20 N outward ✓ Correct
B. 4 N outward
C. 20 N inward
D. 50 N outward
Solution: F = mω²r = 2×25×0.4 = 20 N, directed radially outward in the rotating frame.
Q5 — Centripetal & Centrifugal Force · hard · numerical
A string of breaking tension 100 N whirls a 1 kg stone in a horizontal circle of radius 1 m. Neglecting gravity, the maximum angular speed before the string snaps is:
A. 5 rad/s
B. 100 rad/s
C. 20 rad/s
D. 10 rad/s ✓ Correct
Solution: T = mω²r ⇒ ω_max = √(100/(1×1)) = 10 rad/s.
Q6 — Centripetal & Centrifugal Force · medium · numerical
The centripetal force on a body in UCM is F. If its speed is tripled at the same radius, the required force becomes:
A. F/3
B. 3F
C. 6F
D. 9F ✓ Correct
Solution: F = mv²/r ∝ v² ⇒ ×9.
Q7 — Centripetal & Centrifugal Force · hard · theory
A bead rests on a smooth rotating horizontal rod (rotating about one end). In the ROTATING frame, the bead slides outward because:
A. Gravity acts outward
B. The Coriolis force pushes it outward
C. The centrifugal pseudo force mω²r acts outward with no real force to balance it ✓ Correct
D. A real outward force pushes it
Solution: On a smooth rod nothing supplies the needed centripetal force; in the rotating frame this appears as the unbalanced centrifugal force driving the bead outward. (Coriolis acts perpendicular to the sliding, not outward.)
Q8 — Centripetal & Centrifugal Force · hard · numerical
A gramophone disc spins at ω. A coin at radius r just slips when ω is doubled at the same radius. The friction demand changed by a factor of:
A. 8
B. 2
C. 4 ✓ Correct
D. √2
Solution: Required force mω²r ∝ ω² ⇒ quadruples — exceeding the friction limit that was just sufficient before.