10 years ago I did a pinewood derby car race where you carve out a car from a block of wood. When we were done, my dad cut out some of the bottom of the car and glued in 2 steel weights so that it would roll down the little track faster. It got second out of 20 places and the 1st place winner cheated by cutting their car too thin/aerodynamic.
But now I have learned that all objects on earth accelerate at -9.80 m/s squared due to gravity. So, why did adding the steel masses in my car make it roll down faster than most other cars.
Obviously we aren't simply dropping the cars, so maybe there are some different forces acting on the car, but what would they be?
But now I have learned that all objects on earth accelerate at -9.80 m/s squared due to gravity. So, why did adding the steel masses in my car make it roll down faster than most other cars.
Obviously we aren't simply dropping the cars, so maybe there are some different forces acting on the car, but what would they be?
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______to answer your question pointedly. the cars go faster with weights in them because they now have more weight pulling the car down against the resistances of the bearings and more importantly, the air.
_____in a drag-less world, the math is quite simple, accelleration in a gravitational field is independent of the mass. but in the real world (with viscid air drag and other resistances) mass becomes a central player in how fast something reaches the ground. modeling this is very complex. It must be done numerically with a computer. as a physicist, you will not learn how to properly engage in those calculations until your 3rd year or later. it is beyond the first differential equations class. it is a very MEAN problem. but its sufficient to say that while in air, the heavier you are for a given shape, the faster your terminal velocity will be.
____the deeper answer is both in energetics and momentum physics. if you made the wheels light then they would have no trouble accellerating. in other words. a puck dropped will reach the ground sooner than the same puck rolled down a slope. because the rotational kinetic energy becomes a consumer of the potential energy from the height of the vehicle.
_____if the puck were made to have a smaller and smaller polar moment the puck would get closer and closer to reaching the ground at the same time. you could go a step further. if the track was curvy on its way down, the car *too* will exhibit this same parasitic effect if the weights are not scrunched as close to the center of gravity as was possible. as the body has it's own polar moment of inertia. (i'd look it up on wiki 'moment of inertia')
_____in a drag-less world, the math is quite simple, accelleration in a gravitational field is independent of the mass. but in the real world (with viscid air drag and other resistances) mass becomes a central player in how fast something reaches the ground. modeling this is very complex. It must be done numerically with a computer. as a physicist, you will not learn how to properly engage in those calculations until your 3rd year or later. it is beyond the first differential equations class. it is a very MEAN problem. but its sufficient to say that while in air, the heavier you are for a given shape, the faster your terminal velocity will be.
____the deeper answer is both in energetics and momentum physics. if you made the wheels light then they would have no trouble accellerating. in other words. a puck dropped will reach the ground sooner than the same puck rolled down a slope. because the rotational kinetic energy becomes a consumer of the potential energy from the height of the vehicle.
_____if the puck were made to have a smaller and smaller polar moment the puck would get closer and closer to reaching the ground at the same time. you could go a step further. if the track was curvy on its way down, the car *too* will exhibit this same parasitic effect if the weights are not scrunched as close to the center of gravity as was possible. as the body has it's own polar moment of inertia. (i'd look it up on wiki 'moment of inertia')
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