每日一條physics 題 DSE 5+ 無難度 *Vote in comment 在留言區投票 [3] The bullet aims at the ball, which is at rest high up. When the bullet is fired, the ball is in free fall. Where is the ball when the bullet reaches its highest point(Red Cross)? *blue dotted line is the route of the bullet *white dotted line is the route of the ball 子彈最初瞄準在高處靜止的球。球在子彈發射一刻自由落體。當子彈達到最高點（紅色交叉）時，球在哪個位置？ *藍色虛線是子彈的路線 *白色虛線是球的路線 A:比子彈高 B:與子彈同一高度 C:比子彈稍低 D:兩條路線的相交點

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2024-10-20 05:13

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發文後	用戶	內容
幾秒內	daily_dse_physics
44 分鐘內	daily_dse_physics	*option C should be slightly “lower” than the bullet
3 小時內	equally_shit_69	Step 1:Using s = ut + 1/2gt^2 twice to get displacement of ball when two objects are on the same horizontal level (denote by d1) Step 2: using v= u+ at and s= ut + 1/2 gt ^2 obtain the displacement of two objects Denote by d2 and d3 Steps 3: compare d1 and \|d2\| + \|d3\|
一天內	daily_dse_physics	Answer is A: higher than the bullet First we need to know that the bullet will hit the ball at point D as the gravity acts on both and they have same acceleration. (For your reference) https://youtu.be/0jGZnMf3rPo?si=ge2JEMjrH8IT7-Gg At the bullet's maximum height, its y-component of speed is 0, while the ball's speed remains >0. Thus, they cannot have the same y-displacement after the bullet reaches its peak. The ball must travel a longer displacement, so the answer is A.
一天內	daily_dse_physics	答案是A：比子彈高首先我們需要知道，子彈會擊中 D 點，因為重力作用在兩者上，它們具有相同的加速度。（供您參考） https://youtu.be/0jGZnMf3rPo?si=ge2JEMjrH8IT7-Gg 在子彈的最大高度處，其速度的 y 分量為 0，而球的速度保持 >0。因此，在子彈到達峰值後，它們不能具有相同的 y 位移。球必須移動更長的位移，所以答案是 A。