travel toys in car image
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I was just playing with a toy car of mine. The wheels don't turn on the car, but whenever I pushed it across the kitchen counter, it also turned to the left or the right. Why doesn't it ever go straight?
Answer
i had a similar problem while building a mousetrap car.
the wheels always remain straight, the the car turns.
i found that the problem was because one of the axles of the car was not level with the chassis of the car itself. this was causing more weight to be on one side of the car.
i know its hard to imagine, but if there is more weight on...lets say the left side of the car... it will raise the coefficient of friction on that side essentially making that wheel(s) on that side spin slower. if the left wheels are spinning slower than the right wheels, the right wheels will travel farther, making the car turn.
i had a similar problem while building a mousetrap car.
the wheels always remain straight, the the car turns.
i found that the problem was because one of the axles of the car was not level with the chassis of the car itself. this was causing more weight to be on one side of the car.
i know its hard to imagine, but if there is more weight on...lets say the left side of the car... it will raise the coefficient of friction on that side essentially making that wheel(s) on that side spin slower. if the left wheels are spinning slower than the right wheels, the right wheels will travel farther, making the car turn.
Math - If a toy car that can travel 30 miles per hour, was full sized, How fast would it go?
Blank
The toy car is 1/50 of a regular car.
My 9 year old son is very interested in the answer.
He thinks it would travel 1500 miles an hour if it was full sized.
Would it matter if the car was on a hill?
Answer
All other things being equal, your son is correct. If the scaled up wheels are turning the same number of rpms, the car would go 50 times as fast.
However, there are a number of things that don't scale up in a linear way as you increase the dimensions of a solid, mechanical object, including overall mass, friction, etc.
There is also the minor issue of air resistance and controlling a land vehicle at 1500mph (well more than twice the speed of sound).
I am not sure what you mean by being on a hill. Again, if all other things were equal and the model could go up (or down) the hill at 30 mph, then the scale factor would indicate the full-sized version would travel at 1500 mph. Going up a hill would require additional power to overcome the force of gravity if the car was to maintain its speed, and depending on the grade, that could require quite a lot of horsepower--although maintain the speed under any circumstances against the wind resistance at 1500 mph would be quite a challenge.
In simplest terms, the wind resistance, or drag from the air on a moving body increases with the square of the velocity. So even if the larger car could somehow retain the same dynamic properties as the smaller version (which it wouldn't),
increasing the velocity by a factor of 50 would increase the drag by more than 50^2 = 2500 times. So the engine and the tires, although only 50 times larger than in the model, would somehow have to deliver 2500 times as much force, just to overcome the drag.
All other things being equal, your son is correct. If the scaled up wheels are turning the same number of rpms, the car would go 50 times as fast.
However, there are a number of things that don't scale up in a linear way as you increase the dimensions of a solid, mechanical object, including overall mass, friction, etc.
There is also the minor issue of air resistance and controlling a land vehicle at 1500mph (well more than twice the speed of sound).
I am not sure what you mean by being on a hill. Again, if all other things were equal and the model could go up (or down) the hill at 30 mph, then the scale factor would indicate the full-sized version would travel at 1500 mph. Going up a hill would require additional power to overcome the force of gravity if the car was to maintain its speed, and depending on the grade, that could require quite a lot of horsepower--although maintain the speed under any circumstances against the wind resistance at 1500 mph would be quite a challenge.
In simplest terms, the wind resistance, or drag from the air on a moving body increases with the square of the velocity. So even if the larger car could somehow retain the same dynamic properties as the smaller version (which it wouldn't),
increasing the velocity by a factor of 50 would increase the drag by more than 50^2 = 2500 times. So the engine and the tires, although only 50 times larger than in the model, would somehow have to deliver 2500 times as much force, just to overcome the drag.
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