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.

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
Or = 0.15 mL = 1.5 m1.65 m3.5 kg7 kg

A pendulum is made of a uniform slender rod (3.5 kg, 1.5 m long) pivoted at its top end O, with a thin solid disc of mass 7 kg and radius 0.15 m fixed to its lower end. The disc swings in its own plane and its centre is 1.65 m below O. Find the mass moment of inertia IO of the pendulum about O.

mrod = 3.5 kgL = 1.5 mmdisc = 7 kgr = 0.15 md = 1.65 m
IO = kg·m²
2.Easy
Or = 0.25 mL = 0.5 m0.75 m5 kg6 kg

A pendulum is made of a uniform slender rod (5 kg, 0.5 m long) pivoted at its top end O, with a thin solid disc of mass 6 kg and radius 0.25 m fixed to its lower end. The disc swings in its own plane and its centre is 0.75 m below O. Find the mass moment of inertia IO of the pendulum about O.

mrod = 5 kgL = 0.5 mmdisc = 6 kgr = 0.25 md = 0.75 m
IO = kg·m²
3.Medium
ω = ?3.5 kgL = 0.6 mm = 7 kg

A uniform slender rod of mass 7 kg and length 0.6 m is pinned at one end and released from rest in a horizontal position. A small ball of mass 3.5 kg is fixed to its free end. Ignore friction and use g = 9.81 m/s². Find the angular velocity ω of the rod as it swings through the vertical position.

m = 7 kgL = 0.6 mmball = 3.5 kgg = 9.81 m/s²
ω = rad/s
4.Medium
n = 1500 rpmTb​ = 165 N·mI = 19.5 kg·m²

A flywheel with a moment of inertia of 19.5 kg·m² spins at 1500 rpm. A brake applies a constant friction torque of 165 N·m. How many revolutions N does the flywheel make before it stops?

I = 19.5 kg·m²n = 1500 rpmTb = 165 N·m
N = rev
5.Hard
440 m/s10 g1.13 mL = 1.2 m10 kg

A uniform slender rod of mass 10 kg and length 1.2 m hangs at rest from a frictionless pivot at its top end. A 10 g bullet moving horizontally at 440 m/s hits the rod 1.13 m below the pivot and stays embedded. Find the angular velocity ω of the rod just after the impact.

M = 10 kgL = 1.2 mm = 10 gv = 440 m/sd = 1.13 m
ω = rad/s
6.Hard
θ = 40°a

A hollow sphere 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 = (2/3)·m·r²g = 9.81 m/s²
μs =

Answer key

  1. 1. IO = 21.76 kg·m²
  2. 2. IO = 3.979 kg·m²
  3. 3. ω = 6.264 rad/s
  4. 4. N = 232 rev
  5. 5. ω = 1.033 rad/s
  6. 6. μs = 0.3356

Full step-by-step solutions: practise this topic on examproblems.com.