Which has more kinetic energy: a 0.0016-kg bullet traveling at 398 m/s or a 5.9 107-kg ocean liner traveling at 14 m/s (27 knots)?

Answer 1

The equation for kinetic energy is KE = 1/2mv², where KE is kinetic energy, m is mass, and v is velocity. So we need to solve for the kinetic energy in both cases and compare. Keep in mind, the unit of energy is joules, and 1 J = 1 kg • m² • s^-2

The bullet: KE = (1/2) • (0.0016 kg) • (398 m • s^-1)² = 126.7 kg • m² • s^-2 = 130 J

The ocean liner: KE = (1/2) • (5.9 x 10⁷ kg) • (14 m • s^-1)² = 5.782 x 10⁹ kg • m² • s^-2 = 5.8 x 10⁹ J

The ocean liner has significantly more kinetic energy at 5.8 x 10⁹ J. The liner is significantly more massive, and so, the energy of movement is far greater versus a comparatively itty bitty bullet.