00:01
All right, so it's a cruise ship with a very large mass, right? the mass of this cruise ship is 1 .00 times 10 to the seventh kilograms, right? strikes up here at a speed of three quarters of a meter per second.
00:17
This is bad, right? so our change in velocity is going to be 0 .750 meters per second.
00:25
And it travels six meters, i guess, into the pier or the, yeah, six meters, right? so the distance over which it stops is 6 .0 meters, right? and what they want to know is they want to know the average force exerted on the pier using the concept of impulse.
00:46
And you could use energy, you could use impulse.
00:49
Energy might be easier, but let's use their wishes here.
00:54
So if we want to get a force, right? force times time is going to be mass change in velocity.
01:00
So this is our impulse.
01:04
And what we're saying is that that is equal to the change in momentum.
01:06
So let's play by the rules here.
01:08
Right.
01:09
So the hint that they give us is calculate the time it took to, or the ship to stop, right? okay.
01:15
So the average velocity is going to be 0 .750 plus zero.
01:21
That's its final velocity divided by two.
01:23
And this is assuming, by the way, that it slows down uniformly has a uniform acceleration.
01:29
And they do say average, so let's go for it, right? okay, so this average is 0 .75 divided by 2, which is 0 .375 meters per second.
01:43
So therefore, the time it takes the thing to stop is going to be the distance divided by the average velocity.
01:51
Right? so i'm doing six meters that it travels, right, divided by the average velocity.
01:58
That would give us the time it takes.
02:00
And there's other ways, by the way, to find the time.
02:01
I'm just doing this.
02:03
So six divided by that answer is 16.
02:08
It's going to take 16 seconds...