Question

A 1400 kg car traveling at 17.0 m/s to the south collides with a 4700 kg truck that is at rest. The car and truck stick together and move together after collision. What is the final velocity of the two-vehicle mass? If Kinetic Energy = 0.5 * m * v^2, calculate the KE before the crash and the KE of the combined vehicles after the crash.

Answer 1

Final velocity = 7.677 m/s

KE before crash = 202300 J

KE after crash = 182,702.62 J

Step-by-step explanation:

We are given;

m1 = 1400 kg

m2 = 4700 kg

u1 = 17 m/s

u2 = 0 m/s

Using formula for inelastic collision, we have;

m1•u1 + m2•u2 = (m1 + m2)v

Where v is final velocity after collision.

Plugging in the relevant values;

(1400 × 17) + (4700 × 0) = (1400 + 1700)v

23800 = 3100v

v = 23800/3100

v = 7.677 m/s

Kinetic energy before crash = ½ × 1400 × 17² = 202300 J

Kinetic energy after crash = ½(1400 + 1700) × 7.677² = 182,702.62 J