Physics Ch.9 Test
Distinguish between linear speed and rotational speed
Linear speed- distance covered per time Rotational speed- the number of rotations per time
If the string that holds a whirling can in its circular path breaks, what causes the can to move in a straight-line path--centripetal force, centrifugal force, or a lack of force? What law of physics supports your answer?
A lack of force. This is an example of Newton's 1st Law - the law of inertia.
At a given rotational speed, how does linear (or tangential) speed change as the distance from the axis changes?
As the distance from the axis increases, the linear speed increases. The relationship is directly proportional.
At a given distance from the axis, how does linear (or tangential) speed change as rotational speed changes?
As the rotational speed increases, the linear speed increases. The relationship is directly proportional.
Why is the centrifugal force the ladybug feels in the rotating frame called a fictitious force?
It is a result of rotation. It is not part of an interaction between two objects.
A ladybug in the bottom of a whirling tin can feels centrifugal force pushing it against the bottom of the can. Is there an outside source of this force? Can you identify this as the action force of an action-reaction pair? If so, what is the reaction force?
No. No. There is no reaction force.
Identify the action and reaction forces in the interaction between the ladybug and the whirling can in Figure 9.10.
The can pushes the ladybug inward (centripetal). The ladybug pushes the can outward (centrifugal/inertia).
Does a child on a merry-go-round revolve or rotate around the merry-go-round's axis?
The child revolves around the merry-go-round's axis.
When you whirl a can at the end of a string in a circular path, what is the direction of the force that acts on the can?
The force is toward the center of the circle.
When you roll a cylinder across a surface it follows a straight line path. A tapered cup rolled on the same surface follows a circular path. Why?
The smaller end of the cup travels less distance in one revolution than the large end of the cup. This results in a curved path for the cup.
Does the force that holds the riders on the carnival ride in Figure 9.1 act towards or away from the center?
Towards the center
Does an inward force or an outward force act on the clothes during the spin cycles of an automatic washer?
an inward force
Straight line around which rotation takes place
axis
the straight line around which an object may rotate or revolve
axis
an apparent outward force on a rotating or revolving body. It is fictitious in the sense that it is not part of an interaction but is due to the tendency of a moving body to move in a straight-line path
centrifugal force
center fleeing is
centrifugal force
from within the rotating frame of reference, there seems to be an outwardly directed ___ force, which can simulate ___
centrifugal; gravity
When a car makes a turn, do seat belts provide you with a centripetal force or centrifugal force?
centripetal force
a center-directed force that causes an object to move in a curved (sometimes circular) path
centripetal force
an object moving in a circle is acted on by a
centripetal force
center seeking is
centripetal force
pulls objects toward a center
centripetal force
Increases in speed the further you move out from the axis of a rotating object is
linear speed
the path distance moved per unit of time
linear speed
when an object moves in a circle, there is no force pushing the object ___ from the circle
outward
A satellite is an example of
revolution
motion of an object turning around an axis outside the object
revolution
an object ___ when it turns around an external axis
revolves
an object ___ when turns around an internal axis
rotates
the spinning motion that takes place when an object rotates about an axis located within the object (usually an axis through its center of mass)
rotation
Distinguish between a rotation and a revolution
rotation- when an object turns about an internal axis revolution- when an object turns about an external axis
he number of rotations or revolutions per unit of time; often measured in rotations or revolutions per second or per minute (RPM)
rotational speed
is the number of rotations or revolutions made per unit of time
rotational speed
is the number of rotations per unit of time
rotational speed
Speed along a circular path is called
tangential speed
What is linear speed called when something moves in a circular path?
tangential speed
the speed of an object moving along a circular path
tangential speed
