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AL Physics-Circular motion MC

 

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A car of mass 1000kg approaches a bend at 30 m/s. The bend has a radius of curvature of 0.45km. Take g=10 m / s^2. What angle of banking would just eliminate the frictional forces? 更新: Well, does it mean that if the angle of banking is greater than 11.3 deg., friction from the bend's surface exists?

最佳解答:

Let θ be the angle of banking and R be the normal reaction of the road, then: Vertical component of R (to support the weight of car) = R cos θ, hence R cos θ = mg Vertical component of R (to provide centripetal force for the car) = R sin θ, hence R sin θ = mv2/r Therefore: R sin θ/(R cos θ) = (mv2/r)/(mg) tan θ = v2/(rg) = 302/(10 x 450) = 0.2 θ = 11.3 deg. 2010-09-03 22:51:45 補充： as long as the angle of banking is not 11.3 deg for this case, frictional force exists. If greater than, friction will act upward since R sin θ is too much for cent. force If smaller than, friction will act downward since R sin θ is too less for cent. force

其他解答:0D7DAC4E6DF60DFA

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