00:01
Hello, here a ball is kicked from the ground on the way to a target which is 30 meters away.
00:08
The target is at 1 .8 meters above the ground.
00:13
And the ball is kicked with the initial speed of 35 degrees.
00:17
Here we have to find the initial velocity v0 if the ball spends 2 seconds in air.
00:28
Let's make this sketch.
00:33
Here, v0 is directed at angle alpha.
00:36
The boat travels parabolic trajectory and it completes the flight as the final point.
00:45
So here this motion occurs only under the gravity, therefore l is v0 cosine alpha times time of the flight.
00:52
Now we can calculate v0.
01:19
That is 18 .3 meters per second.
01:23
Now let's find v0 x.
01:25
V0 x is v0 cosign 35.
01:32
That is 15 meters per second and v0y is v0 sign of 35 so therefore in the if you need we can write down this vector v0 as 15 vector i plus 10 .5 j meters per second so now let's move on to the next question in question b we have to calculate velocity when it hits the target so we have to find the final.
02:17
So first let's use a conservation of energy or actually we can probably first calculate v final y.
02:23
V final y is b0y minus g times time of light...