## Posts

Showing posts from October, 2014

### Relative velocity: Boat problems

Problem 1.

A river  flows due East at a speed of 1.3 metres per second. A girl in a rowing boat, who can row at 0.4 metres per second in still water, starts from a point on the South bank and steers due North. The boat is also blown by a wind with speed 0.6 metres per second from a direction of N20ºE.

Find the resultant velocity of the boat and its magnitude.If the river has a constant width of 10 metres, how long does it take the girl to cross the river, and how far upstream or downstream has she then travelled?

Problem 2.

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 to a speed of  5 metres per second.

If you head out pointing your boat at an angle of 90 degrees to the bank. How long does it take to get from point A to point B?After crossing the river you realised that it took  longer than expected. In what direction…