00:01
So here we have a rocket lifting off from a launch pad at a certain force given by the equation.
00:09
Force equals a plus b times times squared a and b are constants that we are going to find in this next step.
00:16
The rocket is equal to 8 kilograms, and at time 1 we have force equals 100 newtons, and at time 2 at 2 seconds, we have force equal to 150 newton.
00:31
So let's begin by first finding a, which will be the easiest one to find.
00:37
So just plugging everything in back to this equation, we have 100 equals a plus b times zero.
00:47
So we have a equals 100 newton's.
00:52
Great.
00:53
Now we can use this to find b.
00:56
So here we have that.
01:04
Remember at time equals t2, we have two seconds.
01:12
And when force equals force two, we have 150 newtons.
01:20
So let's plug this in with what we know.
01:25
100 plus b times square of two.
01:31
So solving for b, f2, minus 100 over t2 squared and just plugging that into that we have 150 minus 100 divided by two squared and we get that b is equal to 12 .5 and newtons per seconds squared so great now we have our second constant so let's notice that the numerator is subtracted of if a subtract of forces that have the si unit of newton's while the denominator is time squared.
02:14
So let's just rewrite this given in the question you want it in si units so we'll rewrite this as f equals 100 plus 12 .5 times squared.
02:32
So going on to the next part of this question, we want to know the net force of the moving rocket and how fast is it accelerating from the launch pad.
02:45
So in order to do this, we want a force diagram for the small rocket, so we can think of this intuitively and then apply the math renal, which is calling for newton's second law.
02:58
So the free body diagram for this would be, say, we have our rocket right here, and we have it is going away from the launch pad.
03:10
The force is going up.
03:12
But remember, it has a specific weight, so that is the force always pulling down.
03:18
So we, it's m -g, so there always that force pulling down to it.
03:25
So let's see.
03:28
So we know newton's second law...