A research team releases a small sealed sensor capsule into a deep column of water. The capsule is denser than water, so it sinks. Fig. 1 shows the capsule ...
Question 1 Report
A research team releases a small sealed sensor capsule into a deep column of water. The capsule is denser than water, so it sinks. Fig. 1 shows the capsule soon after release. At this stage its downward speed is low. As it travels further, water resistance changes because its speed changes. Eventually the capsule falls at a constant speed, allowing the team to predict the time needed for it to reach the measuring station.
Fig. 1
(a) What force makes the capsule begin to move downwards? [1]
(b) Describe how the water resistance changes as the capsule speeds up. [2]
(c) Explain why the capsule later moves at terminal velocity. [3]
(d) Calculate the resultant force on the capsule when it is travelling at terminal velocity. [1]
(e) Sketch a force diagram for the capsule at terminal velocity. Show the directions and relative sizes of weight, upthrust and water resistance. [3]
Answer Details
(a) Weight, the gravitational force, makes the denser capsule start moving downwards. [1]
(b) Water resistance increases as the capsule speeds up because resistance depends on speed through the water. [2]
(c) As speed rises, water resistance rises until the upward forces, water resistance plus upthrust, equal the downward weight. The resultant force is then zero, so there is no acceleration and the capsule continues at constant, terminal velocity. [3]
(d) At terminal velocity, resultant force is \(0\text{ N}\). [1]
(e) The combined upward forces equal the downward weight.
[3]
Download The App On Google Playstore
Everything you need to excel in your exams
