Engineering Mechanics II
Practice Exam #3
1.
Find the requested components of the inertia matrix for the
compound slender bar shown. The bar has a linear density of 3
kg/m. (A slender bar has a moments of inertia about its short axes
about its center of 1/12 M·L2, its moment of inertia about its long
axis is zero, and its products of inertia about its center are zero).
Ixx = ___________________ kg·m2
Iyy = ___________________ kg·m2
Iyz = ___________________ kg·m2
2.
A certain rigid body has an inertia matrix with components given below, (also given in matrix form).
What is the body’s moment of inertia if it is spun about an axis in the direction û , also given below?
Ixx=20, Iyy=15, Izz=10, Ixy=0, Ixz=5, Iyz=5 (all in kilogram meters squared)
 20 0  5


[I]=  0 15  5 kg·m2
 5  5 10 
3.
3 / 5 
û   0 
4 / 5
A certain rigid body has an inertia matrix with components given below, (also given in matrix form).

What is the body’s angular momentum vector if it is spun with angular velocity  , also given below?
Ixx=20, Iyy=15, Izz=10, Ixy=0, Ixz=5, Iyz=5 (all in kilogram meters squared)
 20 0  5


[I]=  0 15  5 kg·m2
 5  5 10 
4.
1
  1 rad/sec
1

A certain rigid body has an inertia matrix with components given below, (also given in matrix form).

What is the body’s rotational kinetic energy if it is spun with angular velocity  , also given below?
Ixx=20, Iyy=15, Izz=10, Ixy=0, Ixz=5, Iyz=5 (all in kilogram meters squared)
 20 0  5


[I]=  0 15  5 kg·m2
 5  5 10 
MAE-2104
1
  1 rad/sec
1

1
Ver. D, Rev 1
Engineering Mechanics II
Practice Exam #3
5.
A disk of mass 12 kg and radius R=0.5 m begins at rest. Forces A=100 N,
B=200 N, and C=300 N (all perpendicular to the disk) act on the disk at
time t=0. Find the acceleration of the center of mass of the disk and its
angular acceleration at this instant. If the forces continue to act in the
same direction relative to the disk, what is its angular velocity vector at
t=2 s? [Moment of inertia through the center of mass and about the z axis
is (1/2)*M*R2 and about the x or y axis is (1/4)*M*R2 ].
6.
A 8-kg spinning rod with extendable ends is rotating about an axis perpendicular to its 2 meter length at
a rate of 20 rad/s. The arms then extend so that the rod becomes 3 meters in length. What is the new
spin rate?
7.
At the instant shown, the base of the robotic arm is turning
about the z axis with an angular velocity of 1 =4 rad/s,
1 = 3 rad/s2. Also, the boom
segment BC is rotating at  BC = 8 rad/s, which is increasing
at  BC = 2 rad/s2. The gripper is retracting at a constant rate
which is increasing at
vC=1 m/s
vC =1 m/s relative to the arm.


Calculate the inertial velocity of point C.
(extra) Find the acceleration of point C.
MAE-2104
2
Ver. D, Rev 1