`A` mass `M`, attached to a spring, oscillates with a period of `2 s`. If the mass is increased by `4kg`, the time period increases by one second. Assuming that Hooke's law is obeyed, find the initial mass `M`.

Options

A. 3.2 kg
B. 1 kg
C. 2 kg
D. 8 kg

Answer

A

Explanation

Time period `T=2=2pi sqrt(M/k)`
and `2+1=2pi sqrt((M+4)/k)`
Or `3=2pisqrt((M+4)/k)`
`:.4/9=M/(M+4)`
or `4M+16=9M`
or `M=16/5=3.2kg`