8.3- TERMINAL SPEED Flashcards
What does any object moving through a fluid experience?
force that drags on it due to fluid
What does the drag any object moving through a fluid depend on? (3)
shape of object
its speed
viscosity of fluid
What is the viscosity of fluid?
measure of how easily fluid flows past a surface
What happens to drag force the faster an object travels in a fluid?
greater the drag force on it
How does the speed of an object released from rest in a fluid change?
increases as it falls
As the speed of an object increases as it falls from rest in a fluid, what does this mean for the drag force?
drag force on it due to fluid increases
What is the resultant force on an object as it falls from rest in a fluid?
difference between force of gravity on it (its weight) + drag force
What happens to resultant force as drag force increases? (motion of object falling in fluid)
resultant force decreases
What happens to acceleration as when drag force increases, resultant force decreases?
acceleration becomes less as it falls
What does the object attain when it continues to fall? (motion of object falling in fluid)
attains terminal spped
What is terminal speed? (motion of object falling in fluid)
drag force on it equal + opposite to its weight
What is the acceleration and speed like when at terminal speed? (motion of object falling in fluid)
acceleration then zero
speed remains constant as it falls
Investigating motion of object falling in fluid?
when object released, thread attached to object pulls tape through tickertimer, which prints dots at constant rate on tape
Investigating motion of object falling in fluid: what is the spacing between the successive dots a measure of?
measure of speed of object as dots printed on tape at constant rate
Investigating motion of object falling in fluid: what can be made from the tape?
tape chart to show how speed changes with time
Investigating motion of object falling in fluid: how is the tape chart made?
by cutting tape at each dot + pasting successive lengths side by side on graph paper
What does the results from investigating motion of object falling in fluid show? (2)
speed increases + reaches constant value, which is terminal speed
acceleration at any instant is gradient of speed-time curve
Investigating motion of object falling in fluid: what is the equation for the resultant force at any instant?
F = mg - D
m- mass
D- drag force
Investigating motion of object falling in fluid: equation for the acceleration of the object?
mg - D / m = g - D / m
Investigating motion of object falling in fluid: what is the initial acceleration
g
Investigating motion of object falling in fluid: why is the initial acceleration g?
as speed is zero, + so drag force is zero, at instant object released
Investigating motion of object falling in fluid: what happens to energy at terminal speed?
potential energy of object transferred as it falls, into internal energy of fluid by drag force
What does the top speed of a road vehicle or aircraft depend on?
its engine power + shape
What type of vehicle can reach a higher top speed?
vehicle with streamlined shape can reach higher top speed than vehicle with same engine power that’s not streamlined
What is the equation for the resultant force on a vehicle?
= Fe - Fr
Fe- motive force (driving force)
Fr- resistive force
What is the equation for the acceleration a vehicle?
a = Fe - Fr / m
Fe- motive force
Fr- resistive force
What happens to drag force as speed increases (motion of powered vehicle)?
drag force increases with speed
When is the maximum speed (terminal speed) of a vehicle reached?
when resistive force becomes equal + opposite to engine force, and a=0
