1. Relative Velocity & River Boat Problems
10/3

2. Relative Velocity
When objects move in a medium that moves in respect to an observer the magnitude of the velocity of the moving object with respect to the observer will not be equivalent to the speedometer reading of the object. Motion is relative to the observer.
Airplanes encounter winds that can influence their motion.
River current influences the motion of the boat and carries it down stream
The resultant velocity of the boat is a vector sum on the boat velocity and river velocity.

3. Plane Travel

4. Suppose the river is moving with a velocity of 3 m/s N and the motorboat is moving 4 m/s E.
What is the resultant velocity of the motorboat?
How can we determine the angle (direction) of the resultant?
What would we need to know to determine:
How much time it takes for the boat to travel shore to shore?
What distance downstream the boat reaches the opposite shore?
5 m/s
36.87*

5. Suppose the river is moving with a velocity of 3 m/s N and the motorboat is moving 4 m/s E.
The width of the river is 80 m wide. How much time does it take the boat to travel shore to shore? What distance downstream does the boat reach the opposite shore?
20 seconds (80m/4m/s)
3m/s x 20s = 60 m

6. A motorboat traveling 4 m/s E encounters a current traveling 7 m/s N
A motorboat traveling 4 m/s E encounters a current traveling 7 m/s N. The river is 60 m wide.
What is the resultant velocity of the motorboat? How much time does it take the boat to travel shore to shore? What distance downstream does the boat reach the opposite shore?
R=8.06m/s
Time=8.57s
y=34.29m