Question

A mass m attached to a spring oscillates every 2 sec. If the mass is increased by 2 kg, then time-period increases by 1 sec. The initial mass is

• A. 1.6 kg
• B. 3.9 kg
• C. 9.6 kg
• D. 12.6 kg

Answer 1

Answer: (A)

1.6 kg

Answer 2

$T = 2 \pi \sqrt { \frac { m } { k } }$ $\Rightarrow$ $\frac { 9 } { 4 } = \frac { m + 2 } { m }$

$\Rightarrow m = \frac { 8 } { 5 } \mathrm {~kg} = 1.6 \mathrm {~kg}$