"An electric motor of mass 100 kg is supported by vertical springs which compress by 1 mm when the motor is installed. If the motor's armature is not properly balanced, for what revolutions/minute would a resonance occur?"(adsbygoogle = window.adsbygoogle || []).push({});

I set my frame of reference at the end of the spring. Therefore, F = kx - mg = 0. To get resonance ω must equal ω0 which is √(k/m) or √(g/x). I know g to be 9.82 m/s² and x to be 1 mm. Therefore, √(g/x) = 31.3 rps or 1878 rpm. The book lists 955 rpm, so where did I go wrong?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Resonance problem

**Physics Forums | Science Articles, Homework Help, Discussion**