# Is the textbook wrong? Circular motion and mechanics

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#1
Question: A boy rides his cycle around a circular track with diameter 50m. The track is banked at 20 degrees to the horizontal. There is no force due to friction. By modelling the boy and his bike as a particle of 75kg, find the speed at which the cycle is moving.

Now my answer is 9.4 mps, however the textbook answer is 13.4 mps. The textbook's answer occurs when you take 50m to be the radius, which is false - the diameter is 50m, the radius is 25m. Did the examiner fall for their own trap? Or have I just misinterpreted the question.
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1 month ago
#2
(Original post by theeetimdoherty)
Question: A boy rides his cycle around a circular track with diameter 50m. The track is banked at 20 degrees to the horizontal. There is no force due to friction. By modelling the boy and his bike as a particle of 75kg, find the speed at which the cycle is moving.

Now my answer is 9.4 mps, however the textbook answer is 13.4 mps. The textbook's answer occurs when you take 50m to be the radius, which is false - the diameter is 50m, the radius is 25m. Did the examiner fall for their own trap? Or have I just misinterpreted the question.
We all sometimes forget to replace the diameter with the radius, so this is likely. It's even more likely if it's one of Edexcel's own text books, as they were rushed out of the printers. I sometimes wonder whether Pearson have heard of proof reading.
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