Question

About how fast must a $50.0g$ bullet be travelling to have the same kinetic energy as a $5,000kg$ truck moving at $5.0m/s$?

• A. $500,000m/s$
• B. $500m/s$
• C. $1600m/s$
• D. $50m/s$
• E. $1200m/s$

Answer 1

The correct option is C $1600m/s$

The kinetic energy of a mass $m$ moving at speed $v$ is given by $\frac{1}{2}m{v}^2$

$⟹\frac{1}{2}{m}_1{v}_1^2=\frac{1}{2}{m}_2{v}_2^2$

$⟹v_2=\sqrt{\frac{m_1}{m_2}}{v}_1$

$=\sqrt{\frac{5000}{0.050}}\times 5m/s$

$\approx 1600m/s$