PHY 250 conceptual questions
Consider two children sitting on a merry-go-round, with one closer to the outer edge and one closer to the
center. Which child has a greater angular speed? - correct answerThey both have the same angular speed. The
outside child would move a larger distance each rotation, so his linear speed would be larger but we are asking
about angular velocity.
There are two kinds of acceleration that can occur in rotational motion - tangential and centripetal. What best
describes the difference between these two kinds of acceleration? - correct answerCentripetal acceleration is
towards the center, while tangential is along the edge of the circle.
Two ladybugs of the same mass are on a record that is on a record player. The record player is turned on and it
reaches a constant velocity. If the male ladybug is all the way at the edge and the female ladybug is halfway
between the center and the edge, what can be said about their moments of inertia? - correct answerThe male
ladybug's moment of inertia is four times that of the female's bc I=r^2
Consider two equal masses M attached to the ends of massless rods, of length R, as shown in the figure. Treat
the two masses as point masses, each located at a distance R from the point where the rods touch. What is the
moment of inertia of this system, about an axis perpendicular to the page and passing through the point where
the rods touch? - correct answer2MR^2 bc I=MR^2
Consider the ball shown in the figure, moving in a circle. What is the direction of the angular momentum of the
ball? - correct answerOut of the page. Angular momentum (L) = right hand rule
An ice skater is spinning with her arms out and is not being acted upon by an external torque. - correct
answerfor the following terms
a. When she pulls her arms in close to her body what happens to her angular momentum? - correct answerit
remains unchanged bc angular momentum doesn't change if there is no external torque acting on her
Consider two children sitting on a merry-go-round, with one closer to the outer edge and one closer to the
center. Which child has a greater angular speed? - correct answerThey both have the same angular speed. The
outside child would move a larger distance each rotation, so his linear speed would be larger but we are asking
about angular velocity.
There are two kinds of acceleration that can occur in rotational motion - tangential and centripetal. What best
describes the difference between these two kinds of acceleration? - correct answerCentripetal acceleration is
towards the center, while tangential is along the edge of the circle.
Two ladybugs of the same mass are on a record that is on a record player. The record player is turned on and it
reaches a constant velocity. If the male ladybug is all the way at the edge and the female ladybug is halfway
between the center and the edge, what can be said about their moments of inertia? - correct answerThe male
ladybug's moment of inertia is four times that of the female's bc I=r^2
Consider two equal masses M attached to the ends of massless rods, of length R, as shown in the figure. Treat
the two masses as point masses, each located at a distance R from the point where the rods touch. What is the
moment of inertia of this system, about an axis perpendicular to the page and passing through the point where
the rods touch? - correct answer2MR^2 bc I=MR^2
Consider the ball shown in the figure, moving in a circle. What is the direction of the angular momentum of the
ball? - correct answerOut of the page. Angular momentum (L) = right hand rule
An ice skater is spinning with her arms out and is not being acted upon by an external torque. - correct
answerfor the following terms
a. When she pulls her arms in close to her body what happens to her angular momentum? - correct answerit
remains unchanged bc angular momentum doesn't change if there is no external torque acting on her
