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13 votes
13 votes
Vectors! A ship can sail at 30 km/h in still water. The ship heads due north. The water current is flowing at 10 km/h due east.

a) What is the actual velocity of the ship?

b) What direction does the ship sail in?

User Bessem Mouelhi
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1 Answer

11 votes
11 votes

Answer:

  • a) 31.62 km/h
  • b) 18.4° NE

======================

Given

  • The speed of the ship = 30 km/h,
  • The speed of the current = 10 km/h

A) Actual velocity is found as the sum of two vectors representing the two velocities.

Since the directions are at 90° (N and E), we will use Pythagorean to find the actual velocity.


  • v = √(30^2+10^2)=√(1000)= 31.62 km/h (rounded)

b) Let the direction the ship sails in is x. Use trigonometry to find the angle from the North:

  • tan x = 10/30
  • tan x = 1/3
  • x = arctan (1/3)
  • x = 18.4° NE
User Seancarmody
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2.3k points