Question

Find out the total energy of the system of two $1kg$ masses moving toward each other, one mass with velocity $v_1=10m/s$, the other with velocity $v_2=20m/s$.

• A. $50J$
• B. $150J$
• C. $200J$
• D. $250J$
• E. $400J$

Answer 1

The correct option is D $250J$

Given : $m_1=m_2=1kg$ $v_1=10m/s$ $v_2=-20m/s$

Total energy of the system $E=K.E_1+K.E_2$

$\therefore$ $E=\frac{1}{2}{m}_1{v}_1^2+\frac{1}{2}{m}_2{v}_2^2$

OR $E=\frac{1}{2}\times 1\times (10{)}^2+\frac{1}{2}\times 1\times (-20{)}^2=50+200=250$ $J$