00:01
Hi there, here we have to calculate the result on speed of a motorboat in three situations, a, b and c.
00:06
So let's look at situation a.
00:08
Here the water flows downwards with the speed of u.
00:12
And the motorboat runs at speed of v prime at an angle of 30 degree with the horizontal line.
00:22
So let's complete this figure to parallelogram to find vector v.
00:31
And this is vector v which we have to calculate at the end.
00:36
That is some of vectors v prime and u and first let's look at this angle.
00:51
So here and yeah here to calculate this vector we can use a coordinate approach.
00:58
Let's introduce y coordinate up and x coordinate down.
01:04
So now let's find x coordinate of vector so vx equals to v prime x plus ux.
01:18
V prime x equals to v prime x equals to v prime times cosine of 30 degree and ux is zero because it's perpendicular.
01:33
So that equals to v prime times cosine of 30 degree, which is 50 meters per second times sign of 30 degree let's calculate it that equals to 43 .3 meters per second we'll leave all the decimals for now and we will run later and v y equals to uy plus v prime y so uy is negative u and v prime y is v prime times sign of 30 degree that equals to 25 or negative 25 meters per second plus 50 meters per second times sign of 30 degree.
02:32
That equals to 0.
02:40
Yeah, that is something extremely close to 0 meters per second.
02:49
Therefore, v equals to its x projection, which is 43 .3 meters per second...