Space Time & Motion A.2 Forces & Momentum (id: b874ed7f1)

本题目来源于试卷: Space Time & Motion A.2 Forces & Momentum，类别为 IB物理学

[填空题]
A car enters a horizontal circular roundabout as shown with a speed of ${35kmh^{-1}}$. The radius of the roundabout is 15m.

• State the force which provides the centripetal force for the circular motion of the car.
  1
• Calculate the minimum coefficient of static friction between the tyres of the car and the road for the car to safely complete its motion around the roundabout.  
  3
• State and explain any change in your answer to part (b) if:
  
  • The mass of the car increases.  ----待选择----changeNo change 
    2
  • The road is banked at an angle so that the car is tilted towards the center of the roundabout.
    2
  • The speed of the car increases.
    

参考答案:
空格1: 8.33±3%  空格2: No change 


本题详细解析:
1.Frictional force (between the roaxq :i2 hkn9h6b. rxyr-d and the car tyres)
Weight is not accepted as a response here.
Further Explanation:
It is the force of friction between the road and the tires that provides the force towards the centre of the roundabout. Without friction, the car would not be able to make the turn.

1.No change
The mass of the car impacts the calculation of the frictional force and centripetal force equally/cancels in the calculation.
2.Decrease
The normal force would contribute to the centripetal force, therefore less frictional force would be sufficient.
Further Explanation:
On a banked turn, the normal force will have a component that points towards the centre of the circle. As the centripetal force required is the same as on a non-banked turn, less frictional force is required and therefore a lower coefficient of friction is sufficient.
3.Increase
At a higher speed, a larger centripetal force would be necessary to maintain the circular motion.
Further Explanation:
A higher speed will increase the value of $\frac{mv^2}{r}$
resulting in the need for a higher value for the coefficient of friction $\mu$

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