Question

My team and I have a mousetrap car project, and I thought I'd come here to seek help or advice from any of you who have created a successful car.

I seen this car: http://tinypic.com/r/8z1kaq/8
My friend made it and said it went 14 meters; however, for our class, we need to utilize a lever that pulls the string, which this car doesn't have. I was thinking to hotglue a skewer to the mousetrap arm and then tape one piece of string to the end of the skewer and wrap the other end around the back axle by gluing a toothpick to the axle for the string to wrap onto? Please give me feedback!

Answer 1

try maths section, physics is pretty much dead

Answer 2

Ah, okay thank you~

Answer 3

Physics might be a good section, since this is more physics than pure math.

I've never built one, but it seems neat! You need a lever, though? It seems like the moving piece of the mousetrap is a lever itself. But, if you need to put your own attachment on to it, a skewer might work well! You might want to fasten it with something like duck tape wrapped around the skewer and mousetrap, but only a little tape. The mousetrap's spring should be putting most of its torque into pulling the string!!

Answer 4

Another thing to look out for is the circumference of the axle that the string wraps around. This will determine how many times your wheels can turn for a given length of string that can be pulled by the lever.

There's honestly a lot of specifics in the design to determine the distance... I think I would consider a heavy contraption with big wheels with a decent grip and a large wheel to axle ratio. I haven't thought it all through yet, because I'm short on time. But that plan is built on the idea (hopefully correct) that spending a lot of time under the torque of the mousetrap with large wheels will give the car a lot of momentum to keep it going to victory.

But a lighter car could have a much greater acceleration, which will be good also.

I think the main issues are terrain and friction between the axle and what holds it, though.
The terrain:
Large radii wheels will not be pushed back on abrupt bumps (like a rise due to the seam of a tile) as much as smaller radii. Think about holding pencil on the ground. Roll a pool ball versus a basketball (I think they have similar mass?). The radii matter. Momentum also helps here.
Friction:
This is big. With flat ground, and no friction, any car could go on for a LONG time.But there is friction. Minimize that by taking advantage of appropriate lubricants or greases. You can also minimize the force of friction by reducing the normal force. I bet you've learned \(\large F_f=F_N\mu\). If the body of the car is light, then it won't put much weight on the axles. Another options is ball bearings of some sort, but that might be more involved!

Answer 5

By the way! I don't know if you would have learned this yet or not, but the wheels have \(\it angular\ momentum\). This depends on how heavy the wheels are and how the mass is distributed.

I don't know how much free time I'll have after today, but feel free to ask any questions about what I've said.