00:01
All right, so in this first part, in part a, we're using that graph to figure out the height when the time was zero, five seconds, and seven seconds.
00:12
So let's go a, we're looking for at time equals zero, five seconds, and seven seconds.
00:21
And so the graph looks a little something like this, where it's gonna start at maximum energy, and the maximum energy is this amount right here.
00:30
And so for the first one, for t equals zero, zero seconds, our potential energy is going to equal the total energy.
00:43
So the potential energy, mgh, is gonna equal 2918 .23, and then we just divide both sides by mg to get the height.
01:00
So 2918 .23 divided by 75 kilograms times 9 .8, we get a height of 3 .97 meters.
01:14
So that's our maximum height, that's the height at t equals zero.
01:19
Now at t equals five, it looks like we have gone up and down a couple times, and now we're right here on our way down, and it looks like it lines right up with 2500 joules.
01:35
So at that five second mark, our potential energy is 2500 joules.
01:41
So 25 joules is our potential energy.
01:45
So at t equals five seconds, potential energy is gonna equal 2500 joules.
01:53
So we've lost some energy as we've gone down, and then we just use the same equation, so mgh, and then divide both sides by mg.
02:05
So h is equal to 2500 divided by 75 times 9 .8, and we get a height of 3 .4 meters.
02:16
So that is at time equals five seconds.
02:22
Now at time equals seven seconds, it looks like we have come down, and we're right at the tippy top basically again...