Question

From the given figure, velocity of block at t=10 sec is
(g = 10 m/$s^2$)

• A. 0 m/s
• B. 6 m/s
• C. 8 m/s
• D. 12 m/s

Answer 1

The correct option is C 8 m/s

Block will move when $F>f_l$
$4t>0.8\times 4\times 10\Rightarrow t>8$
$a=F-f_l\Rightarrow \frac{dv}{dt}=4t-32$
${\int }_0^{v}dv={\int }_8^{10}(4t-32)dt\Rightarrow v=(2t^2-32t{)}_8^{10}$
$v=(2\times {10}^2-32\times 10)-(2\times 8^2-32\times 8)$
$v=(200-320)-(128-256)\Rightarrow v=8m/s$