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 = 0.2 mL = 1.5 m1.7 m5 kg9.5 kg

A pendulum is made of a uniform slender rod (5 kg, 1.5 m long) pivoted at its top end O, with a solid sphere of mass 9.5 kg and radius 0.2 m fixed to its lower end. The centre of the sphere is 1.7 m below O. Find the mass moment of inertia IO of the pendulum about O.

mrod = 5 kgL = 1.5 mmsphere = 9.5 kgr = 0.2 md = 1.7 m
IO = kg·m²
2.Easy
L = 0.6 mGOd = 0.2 mm = 8 kg

A uniform slender rod of mass 8 kg and length 0.6 m rotates about an axis O perpendicular to the rod, 0.2 m from its centre G. Find its mass moment of inertia IO about that axis.

m = 8 kgL = 0.6 md = 0.2 m
IO = kg·m²
3.Medium
n = 300 rpmT = 1800 N·m

A motor delivers a torque of 1800 N·m at 300 rpm. Find its power output P in kW.

T = 1800 N·mn = 300 rpm
P = kW
4.Medium
v = ?4.5 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 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 = 0.6 mmball = 4.5 kgg = 9.81 m/s²
v = m/s
5.Hard
θ = 35°a

A solid cylinder rolls without slipping down a slope inclined at 35° to the horizontal. Use g = 9.81 m/s². Find the acceleration a of its centre.

θ = 35°I = ½·m·r²g = 9.81 m/s²
a = m/s²
6.Hard
580 m/s35 g0.86 mL = 1.4 m4 kg

A uniform slender rod of mass 4 kg and length 1.4 m hangs at rest from a frictionless pivot at its top end. A 35 g bullet moving horizontally at 580 m/s hits the rod 0.86 m below the pivot and stays embedded. Find the angular velocity ω of the rod just after the impact.

M = 4 kgL = 1.4 mm = 35 gv = 580 m/sd = 0.86 m
ω = rad/s

Answer key

  1. 1. IO = 31.36 kg·m²
  2. 2. IO = 0.56 kg·m²
  3. 3. P = 56.55 kW
  4. 4. v = 3.712 m/s
  5. 5. a = 3.751 m/s²
  6. 6. ω = 6.615 rad/s

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