本题目来源于试卷: 2007美国US F=MA物理竞赛，类别为 美国F=MA物理竞赛
[单选题]
When the speed of a rear-f ;ehwks1.y 8udrive car is increasing on a horizontal road, the direcw1k. 8fye;s hub r p(f-4w*lqltion of the frictional force on the tireslq* 4w flbp-(r is
A. backward on the front tires and forward on the rear tires.
B. forward on the front tires and backward on the rear tires.
C. forward on all tires.
D. backward on all tires.
E. zero.
参考答案: A
本题详细解析:
The rear tires are the "drive" tires.
The engine causes them to rotate, and ths2wc,le.y f5w5u,;ty5 kqql qey push *backward* on the road.
By Newton's third law, the road exerts a *forward* static friction force on the rear tires, which accelerates the car.
The front tires .yqqf5wlc5 ; 5wyt,qelu,2 skare passive. As the car accelerates forward, the front tires are "pushed" into rolling.
The road exerts a small *backward* frictional force (rolling friction, or static friction opposing the change in rotation) on them.
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