Physics Help?

Physics Help?

Postby Griffin » Sat Jul 02, 2011 10:18 am

Since I know some of you are scientific and stuff, I figured it would be worth a shot asking this here:

The problem:

I have a toy car with a flywheel/ friction motor thing. I released it from a ramp and measured the distance it travelled from different heights from the end of the ramp. What I need to do is to somehow find out how much of this distance is attributable to the flywheel and how much is attributable to the act of it rolling down the ramp. Is this actually possible?
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Re: Physics Help?

Postby Mikey » Sat Jul 02, 2011 12:16 pm

Just the distance? I'm not sure, as gravity alone would bring it all the way down, no matter whether there was another propulsive force.
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Re: Physics Help?

Postby Griffin » Sat Jul 02, 2011 12:24 pm

Distance as in the distance it travels along the floor after coming off the ramp.
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Re: Physics Help?

Postby Griffin » Mon Jul 04, 2011 7:10 pm

I hate to soud needy or possibly even spammy, but I really do need a solution to this, even if its "Thats impossible to do".
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Re: Physics Help?

Postby Lt. Staplic » Tue Jul 05, 2011 12:41 am

well you can figure out how far it would travel based off the force Gravity would put on the object as it fell, anything extra would be the Fly wheel.

The acceleration on the object would be:

a=gsin(theta)

where a is the acceleration due to gravity the object will feel
g is the acceleration due to gravity in free fall (9.81m/s)
theta is the angle between the surface of the ramp the object is falling down, and the floor.

find the time, t, it takes for it to hit the floor from where it's dropped and you can find the velocity it should have if it was gravity alone:

v=at

then if you have the coefficient of friction for what-ever surface your floor is made out of you can find the distance it should travel alone as:

dx = V(t)+.5at^2

where dx is the distance it should travel
V and t are the same from above,

a is the deceleration due to friction which can be found by ((mu)(Fn))/(m)
mu is the coefficient of friction
Fn is the normal force
and m is the mass of the car.

This is just one way to do it, and I'll admit it seems rather long and tedious, your best bet would be to talk to Graham, IIRC he's a physics teacher and would probably know a better way of doing this than me and my Physics I: Intro to Mechanics course.
Check this out, Let me know if your interested: viewtopic.php?f=33&t=7385
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Re: Physics Help?

Postby Griffin » Tue Jul 05, 2011 6:19 am

Lt. Staplic wrote:This is just one way to do it, and I'll admit it seems rather long and tedious, your best bet would be to talk to Graham, IIRC he's a physics teacher and would probably know a better way of doing this than me and my Physics I: Intro to Mechanics course.


No need, this has helped me enough, Thank you! :)
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Re: Physics Help?

Postby Lt. Staplic » Tue Jul 05, 2011 3:19 pm

no problem
Check this out, Let me know if your interested: viewtopic.php?f=33&t=7385
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Re: Physics Help?

Postby Thorin » Mon Jul 11, 2011 9:36 pm

Staplic's method is correct, although conservation of energy (neglecting friction assuming it doesn't come too near terminal velocity) is an easier way to do it; potential (mass x 9.81 x height) -> kinetic (0.5 x m x v^2). The difference is due to the fly wheel.
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Re: Physics Help?

Postby Lt. Staplic » Tue Jul 12, 2011 5:16 am

dang.......should thought of that one, that is a whole lot simpler....
Check this out, Let me know if your interested: viewtopic.php?f=33&t=7385
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