# Class Project: Marble Ball Launcher [Help]

#### ValerieL

Post moved from the technical forums, so no Homework Template is shown
What I'm here to find out:
I am in the early stages of a physics project to build a electric circuit or use an electrical source to power the force that will carry a marble throughout the mechanical portion of the project, going through linear acceleration and circular motion. I'm not sure what to use to propel the marble, so that it would go in a straight direction and then rotate in a circular motion on its own without me having to manually push it.

Essentially, the electrical portions should horizontally launches a glass marble so that it starts moving and based on that force, be able to go through circular motion and linear acceleration. I have tried using fan power, but it has to be held closely to the marble and does not consistently roll in a straight direction.

A motor-driven system would probably be the best approach, but I am not sure how to apply. I am hoping that others have done similar things before so they can guide me.

Does anyone have ideas on how I can apply physics to this project and control how the ball goes into circular motion and acceleration after being pushed by the electric circuit?

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#### jackwhirl

Does anyone have ideas on how I can apply physics to this project and control how the ball goes into circular motion and acceleration after being pushed by the electric circuit?
I'm not really clear on the circular motion and acceleration... but could something like a pinball plunger work?

#### anorlunda

Mentor
Gold Member
able to go through circular motion and linear acceleration.
circular motion and acceleration
I too am confused. Can you post the actual and complete project requirements?

#### AZFIREBALL

Will this meet the criteria?
Motor compresses a spring which is released to shoot the ball around a circular track (three rails).
At the end of the track the ball falls to the floor, accelerated, by gravity, in a vertical direction.

#### Asymptotic

circular motion and linear acceleration
Similar to a thrown baseball, linear (between pitcher and catcher) but with a certain amount of spin (circular motion)?

#### ChemAir

Gold Member
Would a linear motor operated trebuchet accomplish what you want?

#### some bloke

If I am reading this right, you are after a means to fire a marble in a straight, horizontal motion, whilst it is also made to spin?

The solution to this is quite dependant on several thing which we don't know;

Is the marble rolling on a surface or launched in air?
What angle is the axis of rotation relative to the direction of launch? Is the marble spinning like a bullet, which may be accomplishable using rifling, or is it rolling forwards, rolling backwards, spinning like a top?

The closest thing I can read into your experiment, based on the phrase "does not consistently roll in a direction" is that you are trying to roll a marble along a surface.

Your best option for this is probably to use a fan system, but to do so within a confined tube to maintain the pressure behind the marble. To lessen the risk of the marble skidding instead of rolling, use a rubberised surface to roll along - skidding would be the force of the push overcoming that of friction.

A rubberised surface (perhaps electrical tape) with a guide rail either side of the marble to maintain a straight line, all housed under a half-tube (EG guttering) with the "blow" nozzle of a vacuum cleaner to push it along would probably work.

Alternatively, put a downpipe connector and an end piece on the guttering, and suck the marble towards that end using the vacuum cleaner, if you don't have a "blow" function on the cleaner. Put a mesh over the downpipe connector (which will be pointing up, remember) as added insurance to not lose your marble. This won't allow the marble to exit the "launcher" without some clever adjustments, though.

"Class Project: Marble Ball Launcher [Help]"

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