Question

A block of mass 2 kg is free to move along x-axis. It is at rest and $t=0$ on wards it is subjected to time dependent force $F\left(t\right)$ in the x-direction. The force $F\left(t\right)$ varies with t as shown in figure. Find the kinetic energy of the block after 4.5 s.

• A. 5.06 J
• B. 4.50 J
• C. 7.50 J
• D. 12.20 J

Answer 1

The correct option is A 5.06 J

Area under $F-t$ graph $=$change in momentum=$\Delta P=\frac{1}{2}(4\times 3)-\frac{1}{2}\times \frac{4}{5}\times 1.5=4.5$

$\therefore \frac{P^2}{2M}=5.06J$