PHYS 217 Final, Fall 1999
American University of Beirut · Mechanics · 1 page
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Physics 217 Feb. 20, 1991
Final Exam Time : 2hrs
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1. A turntable rotates with a constant angular velocity (w ) about a perpendicular
axis through its center 0. The position of a point P which is moving relative
10% to the turntable is given by: r = xi + y j where the unit vectors i and j are
fixed in the turntable.
Find : a) The absolute velocity and
b) The acceleration of P in terms of its motion relative to the
turntable.
A mass (m,) hangs from a spring with a constant (k). The point of support of
the spring moves with a horizontal displacement
x, = A sinw t
From (m,) hangs a massless rod of length (L) at the end of which is a second
mass (m5) + The spring moves vertically and the rod is constrained to a vertical
plane.
a) Write the Lagrangian
b) Determine the equations of motion
c) If (@ ) is the angle that the rod makes with the vertical, check the
equations from part (b) if it is assumed that 0 = §=%8= 0 at all times.
Find the Hamiltonian equations of motion for a particle in a central field.
Are there any constants of the motion ?
Find the principal axes and their associated moments of inertia for a cube of
mass M and sides a, for an origin at one corner with axes directed along the
edges of the cube.
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A. For a central force given by F (r) =K -©& ear, kK <0 4 :
2
What values of r are necessary for stable ™ circular orbits ?
The potential energy of a particle moving in one dimension is :
4
“AX
V(x) where (a) is a constant
a) Find the force
b) Discuss the motion qualitatively
Using appropriate symmetries, find the moments of inertia at the center
of a uniform rectangular plate ABCD of sides (Ly) and (Ly).
Also, find the moments of inertia about axes AB and AD and the line
perpendicular to the plate at B.
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