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
R = 0.55 mn = 300 rpm290 kg

A flywheel is a uniform solid disc of mass 290 kg and radius 0.55 m. It spins at 300 rpm. Find its kinetic energy Ek in kJ.

M = 290 kgR = 0.55 mn = 300 rpm
Ek = kJ
2.Easy
k = 0.5 mn = 2100 rpm210 kg

A flywheel of mass 210 kg has a radius of gyration of 0.5 m about its axis. It spins at 2100 rpm. Find its kinetic energy Ek in kJ.

M = 210 kgk = 0.5 mn = 2100 rpm
Ek = kJ
3.Medium
n = 1200 rpmT = 960 N·m

A motor delivers a torque of 960 N·m at 1200 rpm. Find its power output P in kW.

T = 960 N·mn = 1200 rpm
P = kW
4.Medium
n = 2600 rpmTb​ = 145 N·mI = 37.5 kg·m²

A flywheel with a moment of inertia of 37.5 kg·m² spins at 2600 rpm. A brake applies a constant friction torque of 145 N·m. How long t does it take to stop?

I = 37.5 kg·m²n = 2600 rpmTb = 145 N·m
t = s
5.Hard
4.5 m/sω

A solid cylinder of mass 13 kg rolls without slipping at 4.5 m/s. Find its rotational kinetic energy Erot.

m = 13 kgv = 4.5 m/sI = ½·m·r²
Erot = J
6.Hard
9.5 m/sω

A solid cylinder of mass 20 kg rolls without slipping at 9.5 m/s. Find its rotational kinetic energy Erot.

m = 20 kgv = 9.5 m/sI = ½·m·r²
Erot = J

Answer key

  1. 1. Ek = 21.65 kJ
  2. 2. Ek = 1269 kJ
  3. 3. P = 120.6 kW
  4. 4. t = 70.42 s
  5. 5. Erot = 65.81 J
  6. 6. Erot = 451.3 J

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