Lafayette College
Department of Physics
April 7, 2009
Physics 131 LevelIIHomework Set Section 1
Youmay discuss these problems with one or twoother students (or with your instructor), but
your final solutions should be written out by you alone. Under no circumstances should you see
another student’swritten solutions. If you have discussed these problems with anyone you must
acknowledge the collaboration at the beginning of the corresponding problem. Homework is due
in my office by 3:30 PM on the due date and solutions will then be made available on the course
web site. No homework will be accepted after this time.
Youare expected to carefully explain how, starting from basic principles, you have arrivedat
your answers. Please do not use paper with edges frayed from being ripped out of a spiral bound
notebook. If the papers are illegible or disorganized, we reservethe right to return these papers
without being graded. Unless instructed otherwise, all answers should be correct to 3 or 4 sig.
figs.
Assignment 10: Due Monday,April 13, 2009
Problem 1: Consider a large square, length Lon edge, suspended from a vertex(corner) and
rotating in the vertical plane of the square with the axis of the rotation being horizontal. When
the square is at equilibrium, the diagonal passing through the point of suspension is vertical and
defines the
θ
=0position. The mass of the square is Mand the gravitational field is g.
If the square is nowlifted to some angle relative tothe vertical and then released, it will
oscillate back and forth in the vertical plane (ignore anyfrictional effects). Find the ex-
pression for the angular acceleration as a function of
θ
.Does this kinematics fall into any
one of the types that we have studied to date. Explain whyorwhy not.
Assume the square is released from rest from an angle of 90degree.What is the expres-
sion for the angular speed when the square is in the vertical position
θ
=0. Ignore any
frictional effects.
Problem 2: Consider Figure 10-55 in the text. Let the length of each rod be Las in the text,
butlet each rod have a diameter of Dwith D=0. 2 L,with Land unspecified number.Ifthe sys-
tem is released from rest with the H in a vertical position (straight up), what is the linear speed of
the outer tip when it is again vertical but straight down?
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