Question

A spring stretches by 1 mm under a force of 0.9 N. If an unknown mass is attached at its
free end, and the number of oscillations in free vibration recorded in one minute is 600, the
unknown mass is equal to (Take π = 3)
1) 0.5 kg
2) 0.8 kg
3) 0.25 kg
4) 1 kg

Answer 1

I think the actually the answer must be 1 ) 0.5 kg