See rule 4.b.ix
As tasks go, this one is relatively straightforward. It's been a staple of Div B, since they focus on Simple Machines.
The descriptions states that the screw must achieve two tasks: operating as a screw AND moving an object 2cm. I would argue if you bump a ball and simply allow it to roll, gravity is moving the ball for most of that 2cm, not the screw.Do we think that the screw must be in contact with the object it is moving for the whole time? For example, if the screw was moved horizontally only about one centimeter, but made contact with a ball, hitting it and causing it to roll for an additional one or two centimeters, would that satisfy the rules?
I wasn't thinking about using gravity or a ramp. If a screw with wide enough threads is turned fast enough it could hit a small ball and get it to roll across a flat surface. In this case, the screw would be providing all of the energy that the ball needs to move, but the screw would not need to move the full 2 cm itself.The descriptions states that the screw must achieve two tasks: operating as a screw AND moving an object 2cm. I would argue if you bump a ball and simply allow it to roll, gravity is moving the ball for most of that 2cm, not the screw.Do we think that the screw must be in contact with the object it is moving for the whole time? For example, if the screw was moved horizontally only about one centimeter, but made contact with a ball, hitting it and causing it to roll for an additional one or two centimeters, would that satisfy the rules?
Interesting point... As long as the screw undergoes two full rotations, imparts the momentum by acting as a screw, and provides all of the energy to move the object 2cm I think that should be fine.I wasn't thinking about using gravity or a ramp. If a screw with wide enough threads is turned fast enough it could hit a small ball and get it to roll across a flat surface. In this case, the screw would be providing all of the energy that the ball needs to move, but the screw would not need to move the full 2 cm itself.The descriptions states that the screw must achieve two tasks: operating as a screw AND moving an object 2cm. I would argue if you bump a ball and simply allow it to roll, gravity is moving the ball for most of that 2cm, not the screw.Do we think that the screw must be in contact with the object it is moving for the whole time? For example, if the screw was moved horizontally only about one centimeter, but made contact with a ball, hitting it and causing it to roll for an additional one or two centimeters, would that satisfy the rules?
I would interpret this as requiring that all of the kinetic energy required to turn the screw must come directly or indirectly from gravitational potential energy. It does not say the screw must provide said potential energy.What does "Use gravity to clearly rotate a screw" mean? Would dropping a weight that is attached by string to a screw count as using gravity, or does the screw have to somehow turn due simply to its own weight?
I would rely on the simple machine definition of a screw, which incidentally is included directly in the text of 4.b.ix: "converting rotational force into linear force." That does not require it to screw into a solid substrate.What exactly does it mean to operate as a screw? Does it literally have to screw into something, or as long as it rotates, it's fine? Also does the screw itself have to move linearly, or can the screw's rotation cause something that is perpendicular to the screw to move linearly?
Sorry a lot of questions here
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