"Find this stuff." And you're just gonna have to know that okay, if I run off of a cliff horizontally or something gets shot horizontally, that means there is no vertical velocity to start with, I'm gonna have to plug this initial velocity in the y direction as zero. Don't fall for it now you know how to deal with it. But we can't use this to solve directly for the displacement in the x direction.
- [Instructor] Let's talk about how to handle a horizontally launched projectile problem.
These, technically speaking, if you already know how to do projectile problems, there is nothing new, except that there's one aspect of these problems that people get stumped by all of the time.
So if the initial velocity of the object for a projectile is completely horizontal, then that object is a horizontally launched projectile. They're gonna run but they don't jump off the cliff, they just run straight off of the cliff 'cause they're kind of nervous. Alright, fish over here, person splashed into the water.
Let's say they run off of this cliff with five meters per second of initial velocity, straight off the cliff. So 30 meters tall, they launch, they fly through the air, there's water down here, so they initially went this way, and they start to fall down, and they do something like pschhh, and then they splash in the water, hopefully they don't hit any boats or fish down here. We want to know, here's the question you might get asked: how far did this person go horizontally before striking the water?
So this person just ran horizontally straight off the cliff and then they start to gain velocity.
So they're gonna gain vertical velocity downward and maybe more vertical velocity because gravity keeps pulling, and then even more, this might go off the screen but it's gonna be really big. What we know is that horizontally this person started off with an initial velocity.
This person was not launched vertically up or vertically down, this person was just launched straight horizontally, and so the initial velocity in the vertical direction is just zero. They're like "hold on a minute." They're like, this person is gonna start gaining, alright, this person is gonna start gaining velocity right when they leave the cliff, this starts getting bigger and bigger and bigger in the downward direction. We're talking about right as you leave the cliff.
That moment you left the cliff there was only horizontal velocity, which means you started with no initial vertical velocity.
They want to say that the initial velocity in the y direction is five meters per second.
I mean people are just dying to stick these five meters per second into here because that's the velocity that you were given. That's why this is called horizontally launched projectile motion, not vertically launched projectile motion. The initial velocity in the vertical direction here was zero, there was no initial vertical velocity.