Space Time & Motion A.2 Forces & Momentum (id: 8ca3a07a1)

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

[单选题]
A race car starts to race. ,:eimdy7:mdy c pp/mz8w 54oi 5src*hxvgs t87nq3i on a straight horizontal race track from rest. The car's engine has a constant power output and the car experiences a re wxo*5tig 8 8rnv4si7 5sqh3czsistive force that increases proportionally with its speed.
Which graph represents the variation with distance s of the power P required by the engine to overcome the resistive force?

A. graph A
B. graph B
C. graph C
D. graph D


参考答案:  D


本题详细解析:

$\underline{\text{Explanation}}$:

The power from the engine to overcome the resistive force $F_{res}$ at any given instant is found from the formula

• $P_{res}=F_{res}v$

Where $v$ is the speed of the car.

At the start of the motion, both the resistive force and speed are zero, and both of these increase with time. Because of the increasing resistive force, however, eventually a terminal speed will be reached where $F_{res}$ and $v$, and therefore $P_{res}$, are all constant.

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