If you jump out of an airplane, how fast would you fall? What’s the greatest speed you would reach? In a moment, we’re going to find out, but first let’s take a look at objects that are allowed to fall under the influence of just gravity. There are two important things to keep in mind for free falling objects. First, the object doesn’t experience air resistance. Second, the acceleration of the object is a constant value of 9.8 m/s2 or 32.2 ft/s2.
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This lesson may give you a sinking sensation but don’t worry about it. It’s only because we’re talking about gravity. You can’t go anywhere without gravity. Even though we deal with gravity on a constant basis, there are several misconceptions about it. Let’s get to an experiment right away and I’ll show you what I mean.
If I drop a ping pong ball and a golf ball from the same height, which one hits the ground first? How about a bowling ball and a marble?
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Click here to go to next lesson on Velocity.
If acceleration is constant, is velocity also constant? Nope. The image at the top of this page shows that the object is speeding up every second by a certain rate, so velocity is not a constant value. The question is, can we figure out what the speed is at different intervals of time? Of course we can! Here’s how…
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Do you expect a curved or a straight line on a p-t graph for free falling objects? A straight line is the slope of the graph, which is also the velocity. A straight line would mean that the velocity is constant, we we already see from the experiment that it isn’t. So we can expect a curve on our p-t graph that looks like a downhill bunny slope… the object starts out slow, then increases speed so the slope will also increase in “steepness” as time goes on. If we indicate the positive direction as upwards, then the slope on the p-t graph will be negative.
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For constant acceleration, we can expect a straight line on our v-t graph to have a slope of 9.8 m/s2 in the negative quadrant of the graph, starting at the origin. The object started at rest, then finished with a large negative velocity, meaning that the object is speeding up in the downward direction. The constant negative slope means constant negative acceleration. Remember, that negative sign doesn’t mean it’s slowing down, but rather the minus sign indicates which direction the acceleration is happening in.
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If you jump out of an airplane, how fast would you fall? What's the greatest speed you would reach? Let's practice figuring it out without jumping out of a plane.
This experiment will help you get the concept of velocity by allowing you to measure the rate of fall of several objects. It's also a great experiment to record in your science journal.
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You have just taken in a nice bunch of information about the wild world of gravity. This next section is for advanced students, who want to go even deeper. There's a lot of great stuff here but there's a lot of math as well. If you're not a math person, feel free to pass this up. You'll still have a nice understanding of the concept. However, I'd recommend giving it a try. There are some fun things to do and if you're not careful, you might just end up enjoying it!
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If I toss a ball horizontally at the exact same instant that I drop another one from my other hand, which one reaches the ground first? For this experiment, you need: Please login or register to read the rest of this content.
Please login or register to read the rest of this content.
This experiment will help you get the concept of velocity by allowing you to measure the rate of fall of several objects. It's also a great experiment to record in your science journal.
First, you'll need to find your materials: Please login or register to read the rest of this content.
Please login or register to read the rest of this content.
You have just taken in a nice bunch of information about the wild world of gravity. This next section is for advanced students, who want to go even deeper. There's a lot of great stuff here but there's a lot of math as well. If you're not a math person, feel free to pass this up. You'll still have a nice understanding of the concept. However, I'd recommend giving it a try. There are some fun things to do and if you're not careful, you might just end up enjoying it!
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If I toss a ball horizontally at the exact same instant that I drop another one from my other hand, which one reaches the ground first? For this experiment, you need: Please login or register to read the rest of this content.
Please login or register to read the rest of this content.
Click here to go to next lesson on Force and Mass.
We're going to learn more about why gravity accelerates all objects equally when we study Newton's Laws in the next section, where you'll discover how force is related to mass. Right now, here's another set of hints on solving physics problems...
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