soccerball1This experiment is one of my favorites in this acceleration series, because it clearly shows you what acceleration looks like.


The materials you need is are:


  • a hard, smooth ball (a golf ball, racket ball, pool ball, soccer ball, etc.)
  • tape or chalk
  • a slightly sloping driveway (you can also use a board for a ramp that’s propped up on one end)

For advanced students, you will also need: a timer or stopwatch, pencil, paper, measuring tape or yard stick, and this printout.


Grab a friend to help you out with this experiment – it’s a lot easier with two people.


Are you ready to get started really discovering what acceleration is all about?


Here’s what you do:
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1. Place the board on the books or whatever you use to make the board a slight ramp. You really don’t want it to be slanted very high. Only an inch or less would be fine. If you wish, you can increase the slant later just to play with it.


2. Put a line across the board where you will always start the ball. Some folks call this the “starting line.”


3. Start the timer and let the ball go from the starting line at the same exact time.


4. Now, this is the tricky part. When the timer hits one second, mark where the ball is at that point. Do this several times. It takes a while to get the hang of this. I find it easiest to have another person do the timing while I follow the ball with my finger. When the person says to stop, I stop my finger and mark the board at that point.


5. Do the exact same thing but this time, instead of marking the place where the ball is at one second, mark where it is at the end of two seconds.


6. Do it again but this time mark it at 3 seconds.


7. Continue marking until you run out of board or driveway.




Download Student Worksheet & Exercises


Take a look at your marks. See how they get farther and farther apart as the ball continues to accelerate? Your ball was constantly increasing speed and as such, it was constantly accelerating. By the way, would it have mattered what the mass of the ball was that you used? No. Gravity accelerates all things equally. This fact is what Galileo was proving when he did this experiment. The the weight of the ball doesn’t matter but the size of the ball might. If you used a small ball and a large ball you would probably see differences due to friction and rotational inertia. The bigger the ball, the more slowly it begins rolling. The mass of the ball, however, does not matter.


Exercises


  1. Was the line a straight line?
  2. It should be close now, and the slope represents the acceleration it experienced going down the ramp. Calculate the slope of this line.
  3. What do you think would happen if you increased the height of the ramp?
  4. Knowing what you do about gravity, what is the highest acceleration it can reach?

For Advanced Students…

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Now if you want to whip out your calculators you can find out how fast your ball was accelerating. Take your measuring tape and measure the distance from the starting line to the line you made for the distance the ball traveled in one second.


Let’s say for example that my ball went 6 inches in that first second. Dust off those old formulas and lets play with d=1/2gt² where d is distance, g is acceleration due to gravity and t is time.


We can’t use g here because the object is not in free fall, so instead of g let’s call it “a” for acceleration. Gravity is the force pulling on our ball but due to the slope, the ball is falling at some acceleration less then 32 ft/s².


In this case, d is 6 inches, t is 1 second and a is our unknown.


With a little math we see:


a = 12in/sec² (So our acceleration for our ramp is 12 in/sec² or we could say 1ft/s².)


With a little more math we can see how far our ball should have traveled for each time trial that we did. For one second we see that our ball should have traveled d=1/2 12(12) or d= 6 inches (we knew that one already didn’t we?).


For two seconds we can expect to see that d=1/2 12(22) or d=24 inches.
For three seconds we expect d=1/2 12(32) or d= 54 inches.


Do you see why we need a pretty long board for this?


Now roll the ball down the ramp and actually measure the distance it travels after two and three seconds. Do your calculations match your results? Probably not. Our nasty little friend friction has a sneaky way of messing up results. You should definitely see the distance the ball travels get greater with each second however. So make yourself a table or use one of ours to record your data and jot down your calculations and chart your results like a real scientist.


Advanced students: Download your Driveway Races Lab here.


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Comments

16 Responses to “Driveway Races”

  1. Yes, it can look like that. But it can be difficult to tell just by watching. That’s why it is important to use a stopwatch and mark out the distances. That way you can measure how the ball accelerates.

  2. ally_gillotte says:

    hm it looks like it speeds up a lot at the start and speeds up less as time goes on

  3. There are answers to each of the exercises, and you can also ask here! Did you watch the videos that explain acceleration yet?

    When you increase the steepness of the ramp, the acceleration of a soccer ball will also increase when rolls down. Think about it this way: Forces are vectors (which means that they have direction and magnitude), and the force of gravity points straight down from the ball toward the center of the earth. But the ball can’t go straight down to the earth’s core, it has to follow a ramp. That means that only part of the gravitational force (which is the accelerate the ball) points in the same direction as the ball’s motion.

    If the ramp is horizontal, the ball would stay put because all of the gravitational force would be pushing on the ramp which pushes back and there’s no motion in that direction. If the ramp were vertical, the ball would freefall drop with an acceleration due to just gravity. The steeper the ramp, the more the gravitational force is involved in accelerating the ball.

  4. Shelley Reid says:

    We are new to Supercharged Science and haven’t really learned our way around yet. Question number 4 on the excercises asks “what is the highest acceleration it can reach?” We are not sure how to figure out that question. If we don’t understand how to answer a question, where can we go to find the explanation?

  5. Thanks for writing! For this experiment, you’re finding where the ball is at specific intervals in time and learning how to graph it. In the first graph in the worksheet, you are going to graph distance traveled on the vertical and time on the horizontal axes. The slope is rise/run which is distance per time which is speed. (Hint – this should be hard to calculate since the speed starts out slow and then increases more rapidly, so it’s not going to be a straight line.) For the second graph, you’re going to graph distance on the vertical again, but now before graphing the number for time, square it and divide it by 2 first, then graph that number. The slope of the graph is your acceleration, which should now be a straight line. Does that help clarify? It sounds like you have the right idea – just square the time before halving it.

    Aurora

  6. In the first graph are we suppose to just graph the average distance and the time? And for the second graph find out what the acceleration woul be with our average distance, then graph the acceleration with the time/halved?

  8. Colleen Thoresen says:

    Is there a video that takes you through the driveway experiment math? I don’t know how to do the calculations, I’m stuck.

  9. Annette Swartz says:

    I believe you have a typo in this section of the Driveway Races Lab:

    With a little more math we can see how far our ball should have traveled for each time trial that we did. For one second we see that our ball should have traveled d=1/2 12(12) or d= 6 inches (we knew that one already didn’t we?).

    For two seconds we can expect to see that d=1/2 12(22) or d=24 inches.
    For three seconds we expect d=1/2 12(32) or d= 54 inches.

    ————–
    The “2” in the (12) is really (1 ^2) — that is 1 squared. Like wise (22) is (2 ^2) or 2 squared, and (32) is (3 ^2) or 3 squared. Many kids will figure this out without any clarification–if they are really understand the material.

    You could use LaTex to type set your equations and things would be a lot clearer. Just an idea….

  10. Annette Swartz says:

    I noticed that the Advanced Student Driveway Lab does not have the answers to the Acceleration Problems printed in the Solutions section. Are they available somewhere else? My child is doing this lab this week and I’d like to be able to check her answers.

  11. Diana Joubert says:

    Thank you

    -Jacob(10)

  12. Terminal velocity is the fastest velocity balanced by the friction experienced. The greater the friction, the slower the terminal velocity. Does that help?

  13. Nazliatul Aniza Nordin says:

    Hi Aurora!

    So does that mean that the car will hit terminal velocity because of the friction? Will the ball ever hit terminal velocity?

    Thanks!
    -Dayini (12) 🙂

  14. Great question! The car experiences more friction than the ball, because it’s got four points where it contacts the road, and it also has wheel bearings, etc… whereas the ball is just a ball, and the unit moves as a whole, so there’s no loss in energy due to friction through wheels, etc. Also – matchbox race cars are not known for their low-friction wheels, either. 🙂 Does that help?

  15. Nazliatul Aniza Nordin says:

    Hi Aurora!

    I was wondering why this experiment and the ‘Downhill Race’ experiment is similar but have different results? I mean why does the toy car hit terminal velocity but the ball doesn’t?

    Thanks!
    -Dayini (12) 🙂

  16. sevy keble says:

    It is raining right now so I will try it in the morning. This is as awesome as Look Out Below!.
    sevy keble