X is twice as massive as Y. X also runs twice faster than Y. Which one among the following is the ratio of kinetic energy of X and Y ?
[amp_mcq option1=”1 : 8″ option2=”8 : 1″ option3=”4 : 1″ option4=”2 : 1″ correct=”option2″]
This question was previously asked in
UPSC CAPF – 2010
KE_X = ½ * m_X * v_X² = ½ * (2 * m_Y) * (2 * v_Y)² = ½ * 2 * m_Y * 4 * v_Y² = 8 * (½ * m_Y * v_Y²)
KE_Y = ½ * m_Y * v_Y²
The ratio KE_X / KE_Y = [8 * (½ * m_Y * v_Y²)] / [½ * m_Y * v_Y²] = 8 / 1. Thus, the ratio is 8:1.