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As part of an interview for a summer job with the Coast Guard, you are asked to

ID: 1453868 • Letter: A

Question

As part of an interview for a summer job with the Coast Guard, you are asked to help determine the search area for two sunken ships by calculating their velocity just after they collided. According to the last radio transmission from the 50,000-ton cruise ship, the Hangover, it was going due west at a speed of 20 knots in calm seas through the fog just before it was struck broadside by the 70,000-ton ore freighter, the Ironhorse, which was traveling north at 10 knots. The transmission also noted that when the freighter's bow pierced the hull of the liner, the two ships stuck together and sank together.

Explanation / Answer

let Vx and Vy are the components of just after the collision.

Apply conservation of energy in west direction


50000*20 = (50000 + 70000)*vx

==> vx = 50000*20/(50000 + 70000)

= 8.33 knots


Apply conservation of energy in north direction


70000*10 = (50000 + 70000)*vy

==> vy = 70000*10/(50000 + 70000)

= 5.83 knots


so, speed just after the collision,

V = sqrt(vx^2 + vy^2)

= sqrt(8.33^2 + 5.83^2)

= 10.2 knots <<<<<<<<<------------------Answer