IB Physics SL A.1.9 Fluid resistance on projectiles

Track how drag changes a projectile's forces and path so you can predict acceleration, terminal speed and trajectory changes.

Exam points

use the trajectory or force diagram to decide how drag changes height, impact angle or net force
explain terminal speed: drag rises with speed until it balances weight, so acceleration is zero
apply the model assumption mg = kv^2 at terminal speed to calculate k from mass and speed data

[Maximum number: 3]

This question is about kinematics.

After the stone in (a) hits the water surface it rapidly reaches a terminal speed as it falls through the water. The stone leaves Fiona's hand at time t=0. It hits the water surface at $t_{1}$ and it comes to rest at the bottom of the water at $t_{2}$ . Using the axes below, sketch a graph to show how the speed v of the stone varies from time t=0 to just before $t=t_{2}$ . (There is no need to add any values to the axes.)

Figure for Question A.1.9—Fluid resistance on projectiles question 1 — IB Physics SL

Figure for Answer to Question A.1.9—Fluid resistance on projectiles question 1 — IB Physics SL

straight line to water surface;
clear decrease after hitting surface;
constant non-zero speed reached smaller than maximum; $; \begin{aligned} & \text { (speed must be less than } \\ & \text { maximum velocity) }\end{aligned}$

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A.1.9—Fluid resistance on projectiles question 1