MCQs / Physics / Circular and Rotational Motion

Circular and Rotational Motion MCQs — Physics (page 2)

186 multiple-choice questions on Circular and Rotational Motion from Physics, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

26. A car rounds a flat bend of radius 30 m. The coefficient of friction is 0.3 (g = 9.8 m/s^2). The maximum safe speed is:

  1. 4.7 m/s
  2. 13.3 m/s
  3. 18.8 m/s
  4. 9.39 m/s

Answer: D) 9.39 m/s

Explanation: Friction provides the centripetal force: mu mg = mv^2r Rightarrow v = mu g r = 9.39 m/s. SLO P-11-B-15 · Application

Discuss this question

27. A point is 0.5 m from the axis of a wheel rotating at 10 rad/s. Its linear speed is:

  1. 50 m/s
  2. 20 m/s
  3. 5 m/s
  4. 2.5 m/s

Answer: C) 5 m/s

Explanation: v = romega = (0.5)(10) = 5 m/s. SLO P-11-B-08 · Understanding

Discuss this question

28. An ice skater pulls in her arms. Her angular velocity:

  1. increases
  2. decreases
  3. becomes zero
  4. stays the same

Answer: A) increases

Explanation: I decreases, so omega increases to keep Iomega constant. SLO P-11-B-20 · Application

Discuss this question

29. A centrifuge separates particles because:

  1. it makes particles lighter
  2. it heats the mixture
  3. it creates a magnetic field
  4. denser particles need more centripetal force and move outward relative to the liquid

Answer: D) denser particles need more centripetal force and move outward relative to the liquid

Explanation: The liquid cannot provide enough inward force on the denser particles. SLO P-11-B-21 · Application

Discuss this question

30. A flywheel (I = 3 kg m^2) is brought from rest to 12 rad/s in 4 s. The torque needed is:

  1. 18 N m
  2. 9 N m
  3. 4.5 N m
  4. 10 N m

Answer: B) 9 N m

Explanation: alpha = 3 rad/s^2; tau = Ialpha = 9 N m. SLO P-11-B-19 · Application

Discuss this question

31. A 0.5 kg stone on a 1 m string moves in a vertical circle at 4 m/s. The tension at the lowest point is (g = 9.8):

  1. 4.9 N
  2. 3.1 N
  3. 8 N
  4. 12.9 N

Answer: D) 12.9 N

Explanation: At the bottom: T - mg = mv^2r Rightarrow T = 8 + 4.9 = 12.9 N. SLO P-11-B-15 · Application

Discuss this question

32. A diver tucks during a somersault in order to:

  1. slow down the spin
  2. increase moment of inertia
  3. reduce moment of inertia and spin faster
  4. fall faster

Answer: C) reduce moment of inertia and spin faster

Explanation: Same angular momentum, smaller I. SLO P-11-B-20 · Application

Discuss this question

33. If the radius is doubled at the same angular velocity, the centripetal force becomes:

  1. 4 times as large
  2. half as large
  3. twice as large
  4. unchanged

Answer: C) twice as large

Explanation: F = mromega^2 propto r. SLO P-11-B-14 · Application

Discuss this question

34. Objects in a freely falling lift:

  1. float relative to the lift
  2. rise to the ceiling with force
  3. press harder on the floor
  4. fall faster than the lift

Answer: A) float relative to the lift

Explanation: They share the same acceleration. SLO P-11-B-16 · Understanding

Discuss this question

35. 30^circ expressed in radians is:

  1. pi12
  2. 6pi
  3. pi6
  4. pi3

Answer: C) pi6

Explanation: Multiply by pi180^circ: 30 pi180 = pi6 rad. SLO P-11-B-07 · Understanding

Discuss this question

36. A ring of mass 4 kg and radius 0.3 m rotates about its central axis. Its moment of inertia is:

  1. 0.288 kg m^2
  2. 0.36 kg m^2
  3. 0.72 kg m^2
  4. 0.18 kg m^2

Answer: B) 0.36 kg m^2

Explanation: I = MR^2 = 0.36 kg m^2. SLO P-11-B-18 · Application

Discuss this question

37. In a centrifuge, a particle moves outward relative to the tube because:

  1. gravity reverses
  2. a real outward force acts on it
  3. it gains mass
  4. the tube wall pushes on it only when it reaches the bottom; until then it continues tangentially

Answer: D) the tube wall pushes on it only when it reaches the bottom; until then it continues tangentially

Explanation: Inertia, not an outward force. SLO P-11-B-21 · Application

Discuss this question

38. A torque of 10 N m acts on a wheel with I = 2 kg m^2. Its angular acceleration is:

  1. 5 rad/s^2
  2. 2.5 rad/s^2
  3. 10 rad/s^2
  4. 20 rad/s^2

Answer: A) 5 rad/s^2

Explanation: tau = Ialpha Rightarrow alpha = 102 = 5 rad/s^2. SLO P-11-B-19 · Application

Discuss this question

39. An arc of length 3.14 m on a circle of radius 1 m subtends an angle of:

  1. 3.14 rad
  2. 1.57 rad
  3. 6.28 rad
  4. 180 rad

Answer: A) 3.14 rad

Explanation: theta = sr = 3.141 = 3.14 rad. SLO P-11-B-07 · Understanding

Discuss this question

40. At the height of the International Space Station (about 400 km), gravity is:

  1. about 90% of its value at the Earth's surface
  2. twice its surface value
  3. about 1% of its surface value
  4. zero

Answer: A) about 90% of its value at the Earth's surface

Explanation: g falls only slightly at 400 km. SLO P-11-B-16 · Understanding

Discuss this question

41. A stone whirled on a string moves in a circle. The force keeping it on the circle is:

  1. air resistance
  2. the tension in the string, directed to the centre
  3. a centrifugal force outward
  4. its weight only

Answer: B) the tension in the string, directed to the centre

Explanation: Tension provides the centripetal force. SLO P-11-B-10 · Understanding

Discuss this question

42. 45^circ expressed in radians is:

  1. pi4
  2. pi8
  3. 4pi
  4. pi2

Answer: A) pi4

Explanation: Multiply by pi180^circ: 45 pi180 = pi4 rad. SLO P-11-B-07 · Understanding

Discuss this question

43. Why are large-radius rotating stations preferred?

  1. they need no energy
  2. they have stronger real gravity
  3. they are cheaper
  4. they need slower rotation, reducing dizziness

Answer: D) they need slower rotation, reducing dizziness

Explanation: Fast rotation causes motion sickness. SLO P-11-B-17 · Understanding

Discuss this question

44. A ring of mass 10 kg and radius 1 m rotates about its central axis. Its moment of inertia is:

  1. 10 kg m^2
  2. 8 kg m^2
  3. 20 kg m^2
  4. 5 kg m^2

Answer: A) 10 kg m^2

Explanation: I = MR^2 = 10 kg m^2. SLO P-11-B-18 · Application

Discuss this question

45. A torque of 1.2 N m acts on a wheel with I = 0.4 kg m^2. Its angular acceleration is:

  1. 6 rad/s^2
  2. 1.5 rad/s^2
  3. 0.48 rad/s^2
  4. 3 rad/s^2

Answer: D) 3 rad/s^2

Explanation: tau = Ialpha Rightarrow alpha = 1.20.4 = 3 rad/s^2. SLO P-11-B-19 · Application

Discuss this question

46. The Moon moves in a curved path around the Earth because:

  1. no force acts on it
  2. it is pushed by the Sun only
  3. its speed keeps increasing
  4. gravity acts towards the Earth, roughly perpendicular to its velocity

Answer: D) gravity acts towards the Earth, roughly perpendicular to its velocity

Explanation: Gravity provides the centripetal force. SLO P-11-B-10 · Understanding

Discuss this question

47. A car rounds a flat bend of radius 40 m. The coefficient of friction is 0.5 (g = 9.8 m/s^2). The maximum safe speed is:

  1. 19.8 m/s
  2. 28 m/s
  3. 7 m/s
  4. 14 m/s

Answer: D) 14 m/s

Explanation: Friction provides the centripetal force: mu mg = mv^2r Rightarrow v = mu g r = 14 m/s. SLO P-11-B-15 · Application

Discuss this question

48. A rotating space station feels like gravity because:

  1. air pressure pushes down
  2. rotation creates real gravity
  3. the astronaut needs a centripetal force, which the floor supplies as a normal force
  4. the station's mass attracts the astronaut

Answer: C) the astronaut needs a centripetal force, which the floor supplies as a normal force

Explanation: We sense the normal force as weight. SLO P-11-B-17 · Understanding

Discuss this question

49. A body moving in a circle at constant speed is accelerating because:

  1. its speed keeps changing
  2. the direction of its velocity keeps changing
  3. its mass changes
  4. gravity acts on it

Answer: B) the direction of its velocity keeps changing

Explanation: Velocity is a vector. SLO P-11-B-10 · Understanding

Discuss this question

50. A car rounds a flat bend of radius 50 m. The coefficient of friction is 0.8 (g = 9.8 m/s^2). The maximum safe speed is:

  1. 28 m/s
  2. 9.9 m/s
  3. 39.6 m/s
  4. 19.8 m/s

Answer: D) 19.8 m/s

Explanation: Friction provides the centripetal force: mu mg = mv^2r Rightarrow v = mu g r = 19.8 m/s. SLO P-11-B-15 · Application

Discuss this question

Previous Page 2 of 8 Next

Practise Circular and Rotational Motion MCQs

More Physics chapters