Question

a ship sails west at a speed of 10 m/s. a nearby oil tanker sails east at a speed of 11 m/s. in the ships pool, a passenger swims toward the rear of the ship, east, at a speed of 1 m/s. what is the passengers speed toward the tanker relative to the tanker?

Explanation:

Step1: Define velocity directions

Let east - direction be positive. The velocity of the ship $v_{ship}=- 10\ m/s$ (west is negative), the velocity of the tanker $v_{tanker}=11\ m/s$, and the velocity of the passenger relative to the ship $v_{p - ship}=1\ m/s$.

Step2: Use relative - velocity formula

The relative velocity of the passenger with respect to the tanker $v_{p - tanker}=v_{p - ship}+v_{ship}-v_{tanker}$.
Substitute the values: $v_{p - tanker}=1+( - 10)-11$.
First, $1+( - 10)=1 - 10=-9\ m/s$.
Then, $-9-11=-20\ m/s$. The magnitude of the relative - velocity is $20\ m/s$.

Answer:

$20\ m/s$