Scientific Skills & Tools (id: 7c8045601)

本题目来源于试卷: Scientific Skills & Tools，类别为 IB物理学

[单选题]
As a truck is brought to rest, the brakes apply a force of $5.1 \times 10^3N$ Which answer best describes the magnitude of the change in momentum of the truck if the brakes are applied for 3.0s ?

A. 15$\:kN\:s$
B. 15000$\:N\:s$
C. 15.3$\:kN\:s$
D. 15300$\:N\:s$


参考答案:  A


本题详细解析:

Impulse = change in momentum = $F \,t$

So the magnitude of the change in momentum = ($5.1 \times 10^3$)(3.0) = 15300 $N \,s$

All responses match this quantity but the number of significant figures needs to be considered. As both of the values used in the calculation have two significant figures, there should be two significant figures in the answer.

In the answer $15000\,N \,s$, the number of significant figures is unclear. It could be 2, 3, 4 or 5. The response $15\,kN\,s$ clearly has two significant figures, so it is the best answer.

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