Chapters 3 & 4 Flashcards
As you read this in your chair, how fast are you moving relative to the chair? Relative to the Sun?
You are not moving relative to the chair, but you are moving over 100,000 km/h relative to the Sun.
What two units of measurement are necessary for describing speed?
distance & time
s = d/t
What kind of speed is registered by an automobile speedometer?
Instantaneous Speed (speed at any instance)
How can you use the graph of velocity versus time to estimate the acceleration of the ball?
by estimating the value of the slope of the graph
In the video, Dr. Hewitt drops a book and a flat piece of paper together from the same height, and one object hits the ground before the other. Why does that object hit the ground first?
The heavier object–the book–hits the ground first because the other, lighter, object is more influenced by air resistance
what factors determine whether the air resistance experienced by a falling object will affect the motion of the object?
The area of the object in relation to the weight of the object determines the air resistance the object experiences. Objects having greater area but smaller weight experience greater effect of air resistance.
What relationship between distance traveled and time did Galileo discover for freely falling objects released from rest?
Galileo discovered that distance increased as the time squared.
what equation shows that the average speed of a rabbit that runs a distance of 36 m in a time of 3 s is 12 m/s
v = s/t
which equation shows that the acceleration of a hamster is 5 m/s2 when it increases its velocity from rest to 10 m/s in 2 s.
a = deltaV/t
Select the correct equations that show that a freely falling rock drops a distance of 80 m when it falls from rest for 4 s
s = g⋅t2/2 = (10m/s2)⋅(4s)2/2=80m
Acceleration is generally defined as the time rate of change of velocity. When can it be defined as the time rate of change of speed?
When moving in a straight line, the time rate of change of speed is acceleration.
What exactly is meant by a “freely falling” object?
An object in free fall falls under gravity alone with no friction.
A ball is tossed with enough speed straight up so that it is in the air several seconds. Assume upward direction is positive and downward is negative.
0 m/s
3 velocities (m/s)
v = square root of v2 + v2
velocity
speed & direction
~ vector quantity
constant velocity
(constant speed and direction) motion in a straight line at a constant speed
changing velocity
if either speed or direction or both changes, then velocity changes
How does acceleration depend on the net force?
Acceleration is inversely proportional to the net force
If Dr. Hewitt applies 3 N of force to keep the block moving at a steady rate, what must be the force of friction, and why?
Equal to 3 N, because the force of friction should exactly balance out the force Dr. Hewitt applies, so that there is no net force acting on the block.
What general rule can you conclude about the force needed to keep an object in motion at a steady rate?
The force that you need to apply to keep an object moving at a steady rate is equal to the force resisting the motion of the object.
Acceleration (m/s2) depends on
on the net force
To increase the acceleration of an object, you must increase the net force acting on it.
When you apply a force to an object, friction usually
reduces the net force and the resulting acceleration
the force of friction does not depend on
speed
mass
a measure of the inertia of a material object
~ resists acceleration
