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

Answer: (C)

8 m/s

From the above figure, we can say that block can only move if

$F=f$

Frictional force $f=0.8\times 10\times 4=32$ N

And F = 4t

So, we can write

$4t>32$

$Or,t>8$

Now we can write

$a=F-f$

Or, $\frac{dv}{dt}=4t-32$

For finding the velocity at 10 s we have to integrate it

${\int }_0^{v}dv={\int }_8^{10}(4t-32)dt$

After solving this integration we get

$v=8$ m/s

Hence velocity of the block at 10 second is 8 m/s