Rigid-body rotation worksheet with answers

Free printable Rigid-body rotation worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
Or = 0.05 mL = 0.6 m0.65 m4.5 kg2.5 kg

A pendulum is made of a uniform slender rod (4.5 kg, 0.6 m long) pivoted at its top end O, with a thin solid disc of mass 2.5 kg and radius 0.05 m fixed to its lower end. The disc swings in its own plane and its centre is 0.65 m below O. Find the mass moment of inertia IO of the pendulum about O.

mrod = 4.5 kgL = 0.6 mmdisc = 2.5 kgr = 0.05 md = 0.65 m
IO = kg·m²
2.Easy
Or = 0.1 mL = 0.6 m0.7 m0.5 kg8.5 kg

A pendulum is made of a uniform slender rod (0.5 kg, 0.6 m long) pivoted at its top end O, with a thin solid disc of mass 8.5 kg and radius 0.1 m fixed to its lower end. The disc swings in its own plane and its centre is 0.7 m below O. Find the mass moment of inertia IO of the pendulum about O.

mrod = 0.5 kgL = 0.6 mmdisc = 8.5 kgr = 0.1 md = 0.7 m
IO = kg·m²
3.Medium
L = 1.4 mm = 13.5 kgα

A uniform slender rod of mass 13.5 kg and length 1.4 m is pinned at one end and held horizontal. It is released from rest. Use g = 9.81 m/s². Find the vertical force R that the pin exerts on the rod just after release.

m = 13.5 kgL = 1.4 mg = 9.81 m/s²
R = N
4.Medium
v = ?4.5 kgL = 2.2 mm = 7 kg

A uniform slender rod of mass 7 kg and length 2.2 m is pinned at one end and released from rest in a horizontal position. A small ball of mass 4.5 kg is fixed to its free end. Ignore friction and use g = 9.81 m/s². Find the speed v of the free end as the rod swings through the vertical position.

m = 7 kgL = 2.2 mmball = 4.5 kgg = 9.81 m/s²
v = m/s
5.Hard
340 m/s40 g0.2 mL = 0.5 m7 kgφ

A uniform slender rod of mass 7 kg and length 0.5 m hangs at rest from a frictionless pivot at its top end. A 40 g bullet moving horizontally at 340 m/s hits the rod 0.2 m below the pivot and stays embedded. Use g = 9.81 m/s². Find the largest angle φ from the vertical through which the rod swings.

M = 7 kgL = 0.5 mm = 40 gv = 340 m/sd = 0.2 mg = 9.81 m/s²
φ = °
6.Hard
θ = 40°a

A solid cylinder rolls without slipping down a slope inclined at 40° to the horizontal. Use g = 9.81 m/s². Find the smallest coefficient of static friction μs that prevents it from slipping.

θ = 40°I = ½·m·r²g = 9.81 m/s²
μs =

Answer key

  1. 1. IO = 1.599 kg·m²
  2. 2. IO = 4.267 kg·m²
  3. 3. R = 33.11 N
  4. 4. v = 7.109 m/s
  5. 5. φ = 50.71 °
  6. 6. μs = 0.2797

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