Space Time & Motion A.1 Kinematics (id: 26773930f)

本题目来源于试卷: Space Time & Motion A.1 Kinematics，类别为 IB物理学

[单选题]
A cargo container is released from an airplane. A parachute is opened remotely a few seconds later to land it safely. Which graph shows the variation of the vertical acceleration with time t for the cargo container from when it leaves the plane until landing?

A.
B.
C.
D.


参考答案:  D


本题详细解析:

D

Explanation:

The cargo starts with large negative (downward) acceleration. As the cargo container falls, it is speeding up; as it is speeding up, drag force increases, so the acceleration decreases until the cargo container reaches a terminal speed where acceleration is zero. After the parachute is opened, drag force will increase, which is greater than the weight of the cargo container, causing an opposite, upwards, acceleration (deceleration). As the cargo container slows down the drag force decreases, so the net force decreases, and acceleration decreases again until the cargo container reaches a lower terminal speed where acceleration is zero and the forces are balanced.

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