00:01
So we need to split this question into two parts.
00:05
So if we have the hot air balloon, which is moving upwards at 7 metres per second, and a bag is dropped from it.
00:21
So initially it will also have the velocity of 7 metres per second in the upwards direction.
00:31
So it will continue to move upwards.
00:34
And at some point, at some point it's going to stop and then it's going to fall back down again.
00:41
And we want to know the speed when it reaches the floor after it's fallen down.
00:46
So we can split it into two parts, into the first part where it is moving upwards, and to the second part where it is moving downwards.
00:55
So we can work out the distance that it travels upwards, and then we can figure out how far it has to fall back downwards.
01:09
So then we can work out the final velocity of it.
01:16
So we have for the first part, so we need to define our axis.
01:29
So we'll define the positive y direction as going upwards.
01:36
So therefore the initial velocity u is equal to positive.
01:40
7 and the acceleration a is going to equal negative 9 .81.
01:50
Now, we need to consider the final velocity at the maximum altitude.
02:01
So at maximum altitude, it's going to have stopped.
02:05
So right at the, it goes up, up, up, and then right at the moment, right at the moment where it stops there, it's maximum altitude.
02:14
That its velocity in the y direction is equal to zero.
02:20
So it's v is going to equal to zero.
02:23
And we also know the equation for v, so it's going to equal u plus 80.
02:32
So we can work out the time that it's moving upwards for, and then we can use the time to work out the displacement.
02:43
So we know initially it's travelling at 7 meters per second.
02:51
In the outputs direction.
02:54
So we know the final velocity is zero, and we know the acceleration is negative 9 .81, and then this is times by t.
03:06
So then we can use this to calculate two.
03:08
So if i add this over, if i add the 9 .81t over the other side and divide 9 .81, we can see that t is equal to 7 divided by 9 .81, which comes out to 0 .7, 1 seconds.
03:29
So the lunch bag is moving upwards for 0 .71 seconds.
03:35
So we can use this to work out the y position of the the wide position of the bag...