Question

A block of wood of mass 2 kg is lying on the friction less table.A force of 8 N is applied on it for 10 s. Calculate its kinetic energy.

• A. 1600J
• B. 1400 J
• C. 1500 J
• D. 1700 J

Answer 1

The correct option is A 1600J

Acceleration of the block , $a=F/m=8/2=4m/s^2$

Using equation of motion, $S=ut+\frac{1}{2}a{t}^2=0\left(10\right)+0.5\left(4\right)(10{)}^2=200$ m

Now using , $v^2-u^2=2aS$, $v^2-0^2=2\left(4\right)\left(200\right)$

or $v^2=1600$

Thus, KE $=\frac{1}{2}m{v}^2=\frac{1}{2}\times 2\times 1600=1600$ J