Question

The spring block system lies on a smooth horizontal surface. The free end of the spring is being pulled towards right with constant speed V₀ = 2m/s. At t = 0 sec, the spring of constant

k = 100 N/cm is unstreched and the block has a speed 1 m/s to left. The maximum extension of the spring is –

• A. 2cm
• B. 4 cm
• C. 6 cm
• D. 8 cm

Answer 1

Answer: (C)

6 cm

Answer 2

In the frame (inertial w.r.t. earth) of free end of spring, the initial velocity of block is 3m/s to left and the spring unstreched.

Applying conservation of energy between initial and

maximum extension state.

$\frac { 1 } { 2 }$ mV² = $\frac { 1 } { 2 }$ kA²

A = $\sqrt { \frac { \mathrm { m } } { \mathrm { k } } }$ V

$\sqrt { \frac { 4 } { 1000 } }$ × 3 = 6 cm.