phy_ce

The answer is option C
The graph on kinetic energy (KE) is wrong.
The KE curve should increase at a faster rate at first then the rate gradually turns slower until maximum is reached. After the maximum, the KE decreases at a slower rate at first and the rate gradually increases.
The reason is that the rate of change of KE and PE (potential energy) should match with each other. A faster change (decrease) of PE should result in a faster change (increase) of KE. The PE cirve shows a faster decrease at first, following by a slower decrease. Thus, the increase of the KE curve should follow the same pattern.
But the given KE curve indicates a slower rate of increase at first and a faster rate afterwards, which clearly doesn't agree with the PE change.
In fact, the KE curve could be easily obtained by merely flipping over the PE curve about the x-axis, because the sum of the two curves is a constant (straight line).

physics8801 的 answer C 係岩的！
等我翻譯一下，佢話：總能量必定守衡，所以，看得簡單一點，將 PE 圖上下反一反就是 KE圖應有的形狀。
而這個答案，也與我們 k.e. = 1/2 * m * v^2 相吻合，因為一開始的坡度較斜，weight 的vertical component比重較大，所以 rate of increase of 較大，反映在KE圖，即是一開始的slope應較大。

你個答案肯定錯。因為我今日測驗做過，答案係D,我好清楚咁係啊sir 張紙度睇到個答案D!

:D

2009-02-04 22:29:24 補充：
答案係C呢
因為呢個係MOCK EXAM

2009-02-08 00:33:41 補充：
打錯左,,,我冇請人答呢:D

唔知你有冇請人答, SO答喺度:
個KE圖啱嘅, 將KE同PE圖嘅每一點加埋, 你會得到條直線, 即係TOTAL ENERGY, 所以個答案係D。