A river flows due West at a speed of 2.5 metres per second and has a constant width of 1 km. You want to cross the river from point A (South) to a point B (North) directly opposite with a motor boat that can manage a speed of 5 metres per second.
Things to try:

Drag the sliders to change the magnitude and direction of the vectors velocity.

Click the Start button to activate the motion of the boat.

Click the Reset button to put the boat to its original position.

a) If you head out pointing your boat at an angle of 90 degrees to the bank, how long does it take to cross the river? After reaching the bank, how far will the boat be from point B?
b) In what direction should you point your motor boat in to travel directly from point A to point B? How long does it take in such case?