Chapter 4 - Force and Motion - Learning Path Questions and Exercises - Exercises - Page 135: 16

280 N

$F=ma$ Mass is already given. But we need to find the acceleration. When acceleration $a$ is constant $v^{2}=u^{2}+2a(x-x_{0})$. This implies that $a=\frac{v^{2}-u^{2}}{2(x-x_{0})}$ Then, $F=m\times\frac{v^{2}-u^{2}}{2(x-x_{0})}=0.050\,kg\times\frac{(100\,m/s)^{2}-0^{2}}{2\times0.90\,m}=280\,N$