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]
As a truck is broughtz au vfb, 2cem6td2b); tj m+v fhnmn3 z)+9 f+ hjzq,w+;auhvv9o 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 $3.0 \, s$?
A. $15 \, kNs$
B. $15000 \, Ns$
C. $15.3 \, kNs$
D. $15300 \, Ns$
参考答案: A
本题详细解析:
Explannation: Impulse = change in momentum = F t So the magintude of the change in momentun =$(5.1 \times 10^3)(3.0)$ = 15300 $N \, s$ All responses match this quantity but the number of significant figures needs to be considered.As both of values used in the calculation have two significant figures, there should be two significant figures in this 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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