8.3 Terminal speed

Question 1

What does the drag force depend on

Answer 1

The shape of the object
The speed
The viscosity of the fluid, which is a measure of how easily the fluid flows past a substance

Question 2

The faster an object travels in a fluid, the ______ the drag force on it

Answer 2

Greater

Question 3

What is terminal speed

Answer 3

When the drag force on an object is equal and opposite to its weight. Its acceleration is then zero and its speed remains constant as it falls

Question 4

How to investigate the motion of an object falling through a fluid

Answer 4

Tie an object to thread and place above tube of fluid, pass thread over a pulley and connect to a tickertimer.
Release object, pulls tape through ticketmaster
Tickertimer prints dots at a constant rate on the tape, the spacing between successive dots is a measure of the speed of the object

Question 5

What does the top speed of a road vehicle or aircraft depend on

Answer 5

Its engine power and shape
A vehicle with a streamlined shape can reach a higher top speed than a vehicle with the same engine power but not streamlined

Question 6

If FE represents the motive force provided by the engine and FR is the resistive force

Answer 6

a=(FE-FR)/m

Question 7

Why are some hydrofoil boats faster than ordinary voats

Answer 7

They have powerful jet engines that enable them to ski on its hydrofoils when the jet engines are switched on
The hydrofoils extend so the drag force is reduced as its hull is no longer in the water
When the engine is switched off, the hydrofoils retract and the speed drops until the drag force is equal to the motive force of the propeller engine