I was wondering what forces could make the car, while going down the ramp, move away from the surface of the ramp in the x-direction (if x was parallel to the ground)? I was thinking it could be the center of gravity of the car in the x-direction. In other words, the CG is too high above the car. Would this be a reason why my car does this?
Another question, (physics noob), in my opinion, the inertia of the wheel shouldn't affect the exit velocity of the car at the bottom of the ramp by too much. So I think it would be better to use smaller wheels, which increase accuracy, rather than using the 2 3/8 in wheels. So what would be the advantages of using the 2 3/8 in wheels overusing the smaller like 1.5 in wheels?
Also, I tried doing some math, and the max time is 1.81 sec (starting at the top of the ramp). Starting .75 m above would cause the time to only decrease by around .281 sec (this is in the ideal world). The effect will probably be more prominent in the real world so let's just say .5 sec. How will making the CG to the front of the car differ the accuracy of the car? Would this only negatively affect skidding (which is positive)?
Alright I'm a freshman so please don't hate on my bad physics, but I'll try to answer to the best of my abilities.
1. When you mean parallel to the ground, do you mean parallel to the direction of the track, or parallel to the width of the track? If you mean the latter, mass placement does indeed impact the "drift" towards the side. If you mean the former, it is possible that your CG is too high above the car. If it's too high, your car will have tendencies to "pop wheelies", so a little bit in front of the back axle should be the optimal mass placement. Mark Rober goes over this in his Pinewood Derby video.
2. Yes, I think you're correct in saying that smaller wheels will be beneficial. However, imo it's not for the "accuracy" - smaller wheels usually have less mass and therefore less rotational inertia. The heavier wheels are, the more force is required in order to get them spinning. However, if you think about it, smaller wheels will have to rotate more in order to travel the same distance, which makes the friction between the axles and the bearings/bushings a bigger factor. The accuracy you speak for a smaller wheel is pretty much irrelevant if you calibrate to fractions of a wheel rotation.
3. Can't really answer that one, it's way over my head
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