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 = 0.1 mL = 0.7 m0.8 m5 kg1 kg

A pendulum is made of a uniform slender rod (5 kg, 0.7 m long) pivoted at its top end O, with a solid sphere of mass 1 kg and radius 0.1 m fixed to its lower end. The centre of the sphere is 0.8 m below O. Find the mass moment of inertia IO of the pendulum about O.

mrod = 5 kgL = 0.7 mmsphere = 1 kgr = 0.1 md = 0.8 m
IO = kg·m²
2.Easy
R = 0.6 mn = 1100 rpm140 kg

A flywheel is a uniform solid disc of mass 140 kg and radius 0.6 m. It spins at 1100 rpm. Find its kinetic energy Ek in kJ.

M = 140 kgR = 0.6 mn = 1100 rpm
Ek = kJ
3.Medium
n = 600 rpmP = 81.5 kW

A shaft transmits 81.5 kW at 600 rpm. Find the torque T in the shaft.

P = 81.5 kWn = 600 rpm
T = N·m
4.Medium
L = 1.8 mm = 20 kgα

A uniform slender rod of mass 20 kg and length 1.8 m is pinned at one end and held horizontal. It is released from rest. Use g = 9.81 m/s². Find the acceleration atip of the free end just after release.

m = 20 kgL = 1.8 mg = 9.81 m/s²
atip = m/s²
5.Hard
140 m/s30 g0.81 mL = 0.9 m7.5 kgφ

A uniform slender rod of mass 7.5 kg and length 0.9 m hangs at rest from a frictionless pivot at its top end. A 30 g bullet moving horizontally at 140 m/s hits the rod 0.81 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 = 7.5 kgL = 0.9 mm = 30 gv = 140 m/sd = 0.81 mg = 9.81 m/s²
φ = °
6.Hard
disc: 11 kgring: 19 kgn1​ = 500 rpm

A uniform solid disc (mass 11 kg, radius 0.5 m) spins freely at 500 rpm about a vertical frictionless shaft. A thin ring of mass 19 kg and the same radius is dropped onto it from rest, centred on the shaft, and the two quickly spin together. Find their common speed n2 in rpm.

Mdisc = 11 kgMring = 19 kgR = 0.5 mn1 = 500 rpm
n2 = rpm

Answer key

  1. 1. IO = 1.461 kg·m²
  2. 2. Ek = 167.2 kJ
  3. 3. T = 1297 N·m
  4. 4. atip = 14.71 m/s²
  5. 5. φ = 23.78 °
  6. 6. n2 = 112.2 rpm

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