## Objects in Motion

Ask questions about projects relating to: aerodynamics or hydrodynamics, astronomy, chemistry, electricity, electronics, physics, or engineering

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### Objects in Motion

Using a tennis ball, a standard size marble, and a 1 inch diameter ball bearing, on the same measured course, using the same ramp height, will their mass affect their speed?
eporambo

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### Re: Objects in Motion

Theoretically, speed is not affected by the mass of the objects. As you described, if three balls are released on a ramp, they will reach the end of the ramp at the same time. Therefore, the speed of the of the objects are all the same. This is due to the gravitational pull of the Earth on the objects and their ratios of weight to mass. If you were to test this, you may find that the speeds (distance/time) are not exactly the same. Sometimes factors like friction between the objects and the ramp and air resistance may throw your numbers off slightly. However, the speeds should be approximately the same.

Hope this helps and good luck with your experiment!
grai
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### Re: Objects in Motion

While their mass *by itself* will not affect the speed, the *distribution* of the mass *will*. Things rolling on ramps don't behave the same way that things falling through air do.

Their behavior depends on several factors, including density (because of air resistance, mostly), surface qualities (e.g. are they sticky, frictionless, fuzzy, have big air-trapping cones on them , irregular, etc.), and in reference to your question their "moment of inertia".

Moment of inertia, roughly speaking, changes depending on how much of the mass is distributed near the outside of the object, rather than in the middle. You can google or look in wikipedia (though don't use it as a primary source) for a good explanation of what this concept is, though some of these a pretty complicated.

A nice simple explanation of how this applies to objects rolling down ramps can be found here: http://www.batesville.k12.in.us/physics ... e_roll.htm
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Ray Trent
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