sam wants to cross a 80m wide river.the motorboat can travel at 5m/s in still water. he points the boat straight [N] across the river but forgets about the 1.2m/s [E] current. find how far downstream the boat will reach the opposite shore.
the answer is 19.2m
thanks!!!1
2007-03-20 11:37:12 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics
d= v*t he needs to travel 80m north and can travel 5m/s north
80m=5m/s*t
t=16s , he needs to travel for 16 sec to cross the river
since there is a 1.2m/s current east he will be traveling at 1.2m/s for 16seconds.
16s * 1.2m/s = 19.2m
2007-03-20 11:58:53 · answer #1 · answered by jcj7373 2 · 1⤊ 0⤋
Draw a right triangle Such that one side is going up the page and another is going to the left forming a right angle.
The side going up has a value of 5, and the side going left has a value of 1.2
Determine the hypotenuse which equals the square root of the sum of 1.2^2 and 5^2; this equals 5.14. Now tan of angle = 1.2/5 = 0.24
Tan of angle = opposite/adjacent = 0.24=
0.24 = x/80; x= 80 X 0.24
=19.2
2007-03-20 18:59:25 · answer #2 · answered by geo 1 · 1⤊ 0⤋
You know the distance across, and you know how fast he was going. From this you can determine how long it took to cross. Once you know how many seconds it takes to cross, you multiply by the speed of the current to determine how far downstream he is when he reaches shore.
2007-03-20 19:51:11 · answer #3 · answered by rohak1212 7 · 1⤊ 0⤋