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In this episode, we examined what it means to fall and what happens to a falling ball
when you drop it from rest, toss it straight up, or throw it upward at an
angle. We encountered our first force, weight. A ball's weight is the downward
force exerted on it by the Earth's gravity. That weight, it turns out is
exactly proportional to the ball's mass. So that, for every kilogram with the
ball's mass there is, the ball acquires a downward weight of about 9.8 Newtons. That
constant proportionality 9.8 Newtons per kilogram is called the acceleration due to
gravity because not only does it does, does it describe the proportionality
between mass and weight, it also tells you how a ball accelerates if you drop it, if
you allow it to experience only its weight, and therefore accelerate in
response to that weight. That 9.8 Newtons/kg has other units, it's also 9.8
m/s^2, which is explicitly an acceleration. Well, that 9.8 Newtons per
kilogram or meters per seconds squared is true here near the Earth's surface, but if
you go to the moon, the value changes because the strength of gravity on the
moon is different from here near the Earth's surface. Returning back to the
[LAUGH] to, to, to the Earth then, we saw how balls move when they're falling. they
accelerate downward at the acceleration of gravity regardless of which way they're
going, but that downward acceleration causes their velocities to evolve with
time and you see different behaviors, depending on what the balls initial
velocity was. If you drop it from rest, the velocity simply evolves into more and
more downward speed. if you throw it upward the velocity starts upward and so
it's accelerating opposite its velocity. In other words, it's decelerating, so it
slows gradually to a stop, momentarily comes to a true stop and then descends as
though you dropped it from up there and if you throw it up at an angle, well, it's
accelerating straight down, which affects the vertical component of its, of its
velocity and ultimately its position. But it's not accelerating ho rizontally along
a downfield direction so it coasts downfield. And we saw how a lot of ball
sports then make use of this dual behavior. The falling in the vertical
direction and the coasting in the downfield direction. And when you play a
ball sport, you're, you're working with that motion, that dual motion, the rising
and falling, and also the coasting down a field to get what you want, to put the
ball where you want it to be. Well, that's it for balls, for falling balls. go play
some sports and watch the balls fall or, or become one yourself by diving off a
diving board, into the water, of course, which is nice and safe and, you know,
relatively soft. And we'll be back for another episode of how things work.