engineering project

[s to the power of 4]

hey,
we are doing an engineering project for physics and we need to make an elastic powered loonie car. the teacher didnt give us any directions at all and somehow we need to figure out how to drop the loonie. the track is 5m long and the loonie has to drop at 3m and keep going. the loonie cannot be attatched to anything and the mechanism that controls the point at which the loonie is dropped must be self-contained within the car. so if you can please help us on how to make the loonie drop at 3m and keep going?

[CraigD]

Welcome to hypography, s⁴!

Originally Posted by s to the power of 4

we are doing an engineering project for physics and we need to make an elastic powered loonie car. the teacher didnt give us any directions at all and somehow we need to figure out how to drop the loonie. the track is 5m long and the loonie has to drop at 3m and keep going. the loonie cannot be attatched to anything and the mechanism that controls the point at which the loonie is dropped must be self-contained within the car.

For anyone who’s not familiar with Canadian currency, a loonie is a Canadian $1 coin, slightly larger and heavier than a US $0.25 coin

S⁴, if you brows the science projects & homework forum, you’ll find a few sketches and discussions about cars similar to the one you’re designing. The key to the most common kind of design is realizing that thin cord (thread) can be attached to an axle connected to one or more wheels and can either be pulled by an elastic cord (rubber band) etc, or pull something (pin to release a mechanism, sliding block to push a coin off a tray, etc. The details involve calculating and building it, getting the right diameter axle (typically built up with spools or tape) and making or choosing the right diameter wheels, and attaching it all to a chassis with the necessary moving parts.

Try sketching some designs involving thread and axles. I think you’ll find a design for your loonie-dropping car comes fairly quickly.

[s to the power of 4]

OK so how does the loonie drop at 3m and if we attach it to a thin cord wouldn't it be hanging off the cord( we need it to fall onto the ground)then the car has to go another 2m.

[CraigD]

Originally Posted by s to the power of 4

OK so how does the loonie drop at 3m and if we attach it to a thin cord wouldn't it be hanging off the cord( we need it to fall onto the ground)then the car has to go another 2m.

Don’t attach the cord to the coin, attach it to something that pushes the coin.

I'd be easier, I think, if you attach two cords to the pusher, rather than one.

[UncleAl]

Helium lofts 1 gram/liter; ratchet, bottom toggle. Gentle landing triggers severed lines, detensioning triggers propulsion. Navigation is your problem. First... demend increased budget - twonies! Use loonies, keep the excess as untaxable expense chit reimbusements.

[HydrogenBond]

The weight of the falling object, on the string, will wind a spring or rubber band connected to the axle. This will use gravity to store potential energy, within the spring/axle, which will be used later for propulsion, when it touches the ground.

What I would do is simply wind the string around the axle, without actually fastening it to the axle. Like a yoyo without a attachment loop. Maybe a little sandpaper and a tight wind for friction, so the winding does not spin until it is near the ground. The string only has to be long enough to reach the ground and it simply falls off.

[s to the power of 4]

ok so i put the coin on a "tray" or whatt?? and where can i get that from?

[CraigD]

Originally Posted by s to the power of 4

ok so i put the coin on a "tray" or whatt?? and where can i get that from?

I think the idea is for you to build it, not get if from somewhere.

It’s always a challenge in the projects & homework forum to give good hints, without just solving the design problem the project is intended to make the student think about and solve her/himself, so I’ll hint the following:

Try thinking of everyday situation where coins are dropped. For example, put a coin on the table in front of you. Put a book behind it. Now, slowly pull the book toward the edge of the table. You’ll notice that the sliding book causes the coin to fall off the edge of the table at the precise point that the coin is just over half overhanging the edge.

Can you think of a way to build something like this into your rubber band-powered car? Could you use the axle or some other predictably moving part of you car to pull (pulling mechanism are usually easier to build, using string etc., than pushing ones) something equivalent to the book in the above example toward something equivalent to the table edge, making it in such a way that it doesn’t itself fall off the edge (which would, I imagine, be more of hole in the middle of your car) when it continues to be pulled as the car continues moving past where it drops the coin?

Try drawing some pictures. You can post them here by clicking the “manage attachments” button on the “reply to post” page to upload a small image file.