有这样一道常见的习题:“以24米/秒的初速度竖直上抛一个物体,2.0秒后物体到达最高点,试求物体从抛出后经过多长时间落回到抛出点。设物体在整个运动过程中受到的阻力大小保持恒定。”对于这个问题,通常是分别求得上升和下落的加速度,再利用上升和下落的路程相等,可以求出下落的时间 t_2=2.5秒,而上升时间 t_1=2.0秒,整个运动时间 t=t_1+t_2=4.5秒。 There is a common problem: “After throwing an object vertically at an initial speed of 24m/s, the object reaches the highest point after 2.0 seconds. Try to find out how long the object will fall back to the thrown point after throwing. Let’s assume that the resistance of the object during the entire movement is kept constant.” For this problem, the accelerations of ascent and descent are usually obtained respectively, and the distance between rising and falling is equal, and the time of falling can be found t2=2.5 seconds. , And the rise time t_1 = 2.0 seconds, the entire exercise time t = t_1 + t_2 = 4.5 seconds.