Angular Velocity & Acceleration Physics – Chapter 8
In this chapter we discuss angular velocity and acceleration physics – chapter 8
A generalization based upon experiments or observation.
An empirical sceintific law
An essential feature of a scientific theory is…
The making of predictions that can be tested
A meter is —– as long as a kilometer.
1/1000
A large ice cube is 30 cm on each side. If the length of each side is doubled, the surface area increases by a factor of…
4
A large ice cube is 30cm on each side. If the length of each side is tripled, the volume increases by a factor of…
27
1,000,000,000,000 bulls is equal to…
Tbull
10^-6 is equal to…
(Mu)phone
The radius of the earth is 6,380 km at the equator. It’s radius in scientific notation is…
6.38×10^3 meters
Which is faster, a person who can run 100 meters in 10 seconds or a person who can run 100 yards in 10 seconds?
A person who can run at a speed of 10 meters per second
Give an estimate of the number of steps in the stairway of a ten-story building.
10^2
Average speed is calculated by…
Dividing the distance traveled by the elapsed time.
Define acceleration.
The change in velocity with respect to time.
Velocity is what kind of quantity?
A vector quantity
Average speed during a very short time interval is…
Instantaneous speed
The slope of the distance traveled versus time graph is the…
Velocity
The slope of velocity versus time graph is the…
Acceleration
T/F: in the case of uniform accelerated motion, the graph of velocity versus time is a straight line.
True
T/F: in the case of uniform accelerated motion, the graph of distance traveled versus time is a straight line.
False.
T/F: if the acceleration is zero, the velocity is constant.
True
An object undergoing free fall experiences…
A constant acceleration
Just after it is released, an object thrown upward has… (in reference to its velocity and acceleration)
It’s velocity directed upward and it’s acceleration directed downward
Just before it reaches the peak of the path of its motion, an object thrown upward has… (in reference to its velocity and acceleration)
It’s velocity directed upward and it’s acceleration directed downward
After it passes the peak of the path of its motion, an object thrown upward has… (in regards to its velocity and acceleration)
It’s velocity directed downward and it’s acceleration directed downward
Who showed that in the absence of air resistance, all objects fall at the same rate regardless of their weight?
Galileo
Neglecting air resistance, a freely falling object has its velocity…
Increase linearly with time
Neglecting air resistance, a freely falling object has its displacement…
Increase as the square of the time
During every second after an object is dropped from rest and experiences free fall, it’s speed…
Increases by 9.8 m/s
Neglecting air resistance, one second after an object is dropped from rest and experiences free fall, it’s displacement is…
4.9 meters
Neglecting air resistance, one second after and object is dropped from rest and experiences free fall, it’s velocity is…
9.8 m/s
If no force is acting on an object, he object is…
At rest or moving with a constant velocity
According to newtons 2nd law, if the force is doubled and the mass remains the same, the acceleration…
Will double
An ice skater glides across a frozen pond at a constant velocity. What is the net force acting on the skater?
Zero
A single force is acting on an object. Which type of motion is not physically possible?
The object is at rest
If an astronaut takes an object to the moon what will happen to its weight and mass?
The objects weight will change but it’s mass will be the same
This force acts perpendicular to the surface.
A normal force
You stand on a scale that rests on the floor of an elevator that is accelerating upward. What is the relationship between the weight and the normal force exerted by the scale?
The normal force is great than the weight
A unit of force is…
Newton
Terminal velocity is a term used to describe…
The constant velocity a falling object reaches when the net force is zero
A bathroom scale with a person standing on it in an elevator accelerating downward would indicate…
A smaller reading than if the elevator were at rest
the center of all circular paths is defined as …..
axis of rotation
the angle through which an object rotates about a fixed axis
angular displacement
the angular displacement is hte angle ∆θ that is swept out by ……
a line passing through any point on the body and intersecting at the axis of rotation perpendicularly
by convention, the angular displacement is ______ if it is counterclockwise and ______ if it is clockwise
positive if counterclockwise, negative
angular displacement is often expressed in one of three units,
1) degrees
2) revolution
3) radians (rad)
θ in radians =
arc length÷ radius (s/r)
1 rad =
360° / 2π = 57°
Angular velocity describes the motion of…
the motion of a rigid object rotating about a fixed axis
average angular velocity (w) =
angular displacement / elapsed time
angular velocity unit:
rad/s
angular acceleration
changing angular velocity
average angular acceleration =
change in angular velocity / time
angular acceleration unit:
rad/s²
a complete description for rotational motion requires values for the ____, ______, _____,_____and ______
angular displacement ∆θ
angular acceleration α
final angular velocity (w)
initial angular velocity w₀
and elapsed time ∆t
when the angular acceleration is constant, the average angular velocity is given by :
w = 1/2 (w₀ + w)
tangential velocity
vector drawn tangent to appropriate circle
the tangential speed of any skater is directly proportional to the skater’s…
distance R from the pivot
the skater farthest from the pivot must have the largest….
tangential acceleration
the advantage to using angular velocity AND angular acceleration is that….
these angular quantities describe the motion of the entire object
in contrast with angular velocity and angular acceleration, the tangential velocity describe only …..
the motion of a single point on the object
when an object picks up speed as it moves around a circle, it has ______ ________
tangential acceleration
uniform circular motion
object moves at a constant tangential speed on a circular path
even when the magnitude of tangential velocity is constant, an acceleration is present, because
the direction of the velocity changes continuously
when the tangential speed is changing, the motion is called
nonuniform circular motion
the essence of rolling motion is that there is
no slipping at the point of contact where the tire touches the ground
when a rigid object rotates around a fixed axis, it is____ _______ that identifies the motion, and the angular velocity points along……
the axis, this axis
right hand rule
grasp the axis of rotation with your right hand, so that your fingers circle the axis in the same sense as the rotation. your extended thumb points along the axis in the direction of the angular velocity vector
no part of the rotating object moves in the direction of…..
the angular velocity vector
the acceleration vector has the same direction as the ________
change in the angular velocity
when the magnitude of the angular velocity (which is angular speed) is increasing, the angular acceleration vector points in the same direction as the _____
angular velocity