Q160 · Practice questionComplex unfamiliar6 marks
QUESTION 160 (6 marks)
A puck co-rotates with a horizontal turntable at radius . Its period is . Static friction can supply at most . Use a model in which friction is the only horizontal force.
a)[3 marks]
Calculate the required friction force and determine whether the puck slips.
b)[3 marks]
Determine the shortest period for which the puck can co-rotate without slipping.
WORKED SOLUTION
6 marksPractice marking scheme
ANSWER
(a) inward; it does not slip. (b) .
Worked solution
(a) . Required friction is , below . It points toward the centre.
(b) At the limit, . Thus . Smaller periods require greater centripetal force than friction can provide.
Equivalent physically justified methods and consistent equivalent units accepted.
Displayed decimals are model answers; accept appropriate significant figures and consistent rounding from stated constants.
Part a: Calculate tangential speed from period.
Part a: Calculate the required inward force.
Part a: Compare with maximum static friction and conclude no slip.
Part b: Set required centripetal force equal to the friction limit.
Part b: Rearrange for the limiting period.
Part b: Calculate the period and identify it as a minimum.
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