8.3- TERMINAL SPEED

Question 1

What does any object moving through a fluid experience?

Answer 1

force that drags on it due to fluid

Question 2

What does the drag any object moving through a fluid depend on? (3)

Answer 2

shape of object
its speed
viscosity of fluid

Question 3

What is the viscosity of fluid?

Answer 3

measure of how easily fluid flows past a surface

Question 4

What happens to drag force the faster an object travels in a fluid?

Answer 4

greater the drag force on it

Question 5

How does the speed of an object released from rest in a fluid change?

Answer 5

increases as it falls

Question 6

As the speed of an object increases as it falls from rest in a fluid, what does this mean for the drag force?

Answer 6

drag force on it due to fluid increases

Question 7

What is the resultant force on an object as it falls from rest in a fluid?

Answer 7

difference between force of gravity on it (its weight) + drag force

Question 8

What happens to resultant force as drag force increases? (motion of object falling in fluid)

Answer 8

resultant force decreases

Question 9

What happens to acceleration as when drag force increases, resultant force decreases?

Answer 9

acceleration becomes less as it falls

Question 10

What does the object attain when it continues to fall? (motion of object falling in fluid)

Answer 10

attains terminal spped

Question 11

What is terminal speed? (motion of object falling in fluid)

Answer 11

drag force on it equal + opposite to its weight

Question 12

What is the acceleration and speed like when at terminal speed? (motion of object falling in fluid)

Answer 12

acceleration then zero

speed remains constant as it falls

Question 13

Investigating motion of object falling in fluid?

Answer 13

when object released, thread attached to object pulls tape through tickertimer, which prints dots at constant rate on tape

Question 14

Investigating motion of object falling in fluid: what is the spacing between the successive dots a measure of?

Answer 14

measure of speed of object as dots printed on tape at constant rate

Question 15

Investigating motion of object falling in fluid: what can be made from the tape?

Answer 15

tape chart to show how speed changes with time

Question 16

Investigating motion of object falling in fluid: how is the tape chart made?

Answer 16

by cutting tape at each dot + pasting successive lengths side by side on graph paper

Question 17

What does the results from investigating motion of object falling in fluid show? (2)

Answer 17

speed increases + reaches constant value, which is terminal speed

acceleration at any instant is gradient of speed-time curve

Question 18

Investigating motion of object falling in fluid: what is the equation for the resultant force at any instant?

Answer 18

F = mg - D

m- mass
D- drag force

Question 19

Investigating motion of object falling in fluid: equation for the acceleration of the object?

Answer 19

mg - D / m = g - D / m

Question 20

Investigating motion of object falling in fluid: what is the initial acceleration

Answer 20

g

Question 21

Investigating motion of object falling in fluid: why is the initial acceleration g?

Answer 21

as speed is zero, + so drag force is zero, at instant object released

Question 22

Investigating motion of object falling in fluid: what happens to energy at terminal speed?

Answer 22

potential energy of object transferred as it falls, into internal energy of fluid by drag force

Question 23

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

Answer 23

its engine power + shape

Question 24

What type of vehicle can reach a higher top speed?

Answer 24

vehicle with streamlined shape can reach higher top speed than vehicle with same engine power that’s not streamlined

Question 25

What is the equation for the resultant force on a vehicle?

Answer 25

= Fe - Fr

Fe- motive force (driving force)
Fr- resistive force

Question 26

What is the equation for the acceleration a vehicle?

Answer 26

a = Fe - Fr / m

Fe- motive force
Fr- resistive force

Question 27

What happens to drag force as speed increases (motion of powered vehicle)?

Answer 27

drag force increases with speed

Question 28

When is the maximum speed (terminal speed) of a vehicle reached?

Answer 28

when resistive force becomes equal + opposite to engine force, and a=0