A swimmer can swim at 3 km/h in still water. If he swims across a river flowing

Practice Questions

Q1
A swimmer can swim at 3 km/h in still water. If he swims across a river flowing at 2 km/h, what is his resultant speed?
  1. 3 km/h
  2. 4 km/h
  3. 5 km/h
  4. 6 km/h

Questions & Step-by-Step Solutions

A swimmer can swim at 3 km/h in still water. If he swims across a river flowing at 2 km/h, what is his resultant speed?
  • Step 1: Understand that the swimmer's speed in still water is 3 km/h.
  • Step 2: Recognize that the river is flowing at 2 km/h.
  • Step 3: Visualize the swimmer swimming across the river. His speed is at a right angle to the river's flow.
  • Step 4: Use the Pythagorean theorem to find the resultant speed. This is because the swimmer's speed and the river's speed form a right triangle.
  • Step 5: Calculate the square of the swimmer's speed: 3 km/h * 3 km/h = 9.
  • Step 6: Calculate the square of the river's speed: 2 km/h * 2 km/h = 4.
  • Step 7: Add the two results together: 9 + 4 = 13.
  • Step 8: Take the square root of the sum to find the resultant speed: √13.
  • Step 9: Calculate the square root of 13, which is approximately 3.6 km/h.
  • Relative Velocity – Understanding how to calculate the resultant speed of an object moving in a medium with a current.
  • Pythagorean Theorem – Applying the theorem to find the resultant speed when two velocities are perpendicular.
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