2007美国US F=MA物理竞赛 (id: 10d7c0c15)

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]
The graph shows velocityzotl wv9*nzy7.p.+y-fi( l8b pnnw4 p as a functionew cllc8)dgh - qy;xn30vy6 js 9pxv;( of time for a car. What was the accelerationdglc6h;)x8-9 jyw;e cq0lp( 3nvsxy v at time $= 90$ seconds?

A. $0.22\,\mathrm{m/s}^2$
B. $0.33\,\mathrm{m/s}^2$
C. $1.0\,\mathrm{m/s}^2$
D. $9.8\,\mathrm{m/s}^2$
E. $30\,\mathrm{m/s}^2$


参考答案:  B


本题详细解析:
Acceleration is the slope (gradient) of the velo3v9jnb)pfi70qqpmzrfel( .77r tm*t city-time graph. At $t = 90\,\mathrm{s}$, the graph is a straight line. We can find the slope using two points on this linear section, for example, $(t_1, v_1) = (60\,\mathrm{s}, 10\,\mathrm{m/s})$ and $(t_2, v_2) = (120\,\mathrm{s}, 30\,\mathrm{m/s})$. $a = \Delta v / \Delta t = (v_2 - v_1) / (t_2 - t_1) = (30 - 10)\,\mathrm{m/s} / (120 - 60)\,\mathrm{s} = 20\,\mathrm{m/s} / 60\,\mathrm{s} \approx 0.33\,\mathrm{m/s}^2$.

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