Question

A block of 5 kg is pressed adjoint wall by spring (compressed) having k = 1000N/m, if coefficient of friction between block & wall is $\mu$ = 0.8. Find minimum compression in spring so that block remains stationary.

• A. 6.25 cm
• B. 12.5 cm
• C. 3.2 cm
• D. 8.4 cm

Answer 1

The correct option is A 6.25 cm


$f=mg\le \mu N$
$\Rightarrow mg\le \mu KX$
$X\ge \frac{mg}{\mu K}$
$X\ge \frac{5\text{/}0}{0.8\times 100\text{/}0}$
$X_{max}=\frac{1}{0.8\times 20}=\frac{1}{16}=6.25cm$