Optional FE Review: Dynamics
Chris Rehmann
Dynamics
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Kinematics
Mass moments of inertia
Force acceleration (sic)
Impulse momentum
Work, energy, and power
Kinematics: USF question 4.1
Kinematics: AUC exam #74
Kinematics: Angular motion
What are the angular velocity and linear speed
of the tip of a 0.1 m long second hand on a
clock?
a.
b.
c.
d.
1 rad/s, 0.1 m/s
0.1 rad/s, 0.01 m/s
60 rad/s, 0.1 m/s
60 rad/s, 0.6 m/s
Moment of inertia: example 1
The area moment of inertia in
cm4 about the axis A-A’ most
nearly is
A.
B.
C.
D.
2813
1250
11,250
5000
10 cm
15 cm
A
A’
Moment of inertia: example 2
The area moment of inertia in
cm4 about the axis A-A’ most A
nearly is
A.
B.
C.
D.
3050
6050
22,850
24,565
10 cm
15 cm
A’ 7cm
Force & acceleration: Newton’s law
A 5-kg block of steel initially at rest on a steel
plate is subjected to a constant force of 25 N.
The coefficient of friction is 0.4. How far will the
block have traveled in 10 seconds?
a.
b.
c.
d.
4m
24 m
54 m
250 m
Force & acceleration: AUC exam #73
Force & acceleration: USF question 4.2
Force & acceleration: USF question 4.3
Force & acceleration: AUC exam #76
Force & accel.: Uniform circular motion
A curve of radius 500 m at a speedway is banked at
an angle of 22°. If drivers of racecars do not wish to
rely on friction, at what speed should they take this
curve?
a.
b.
c.
d.
50 mph
60 mph
70 mph
100 mph
Ohanian (1985), ch. 6, ex. 13
Force & acceleration: Angular & linear motion
Two masses are suspended from a string that
runs without slipping over a pulley of radius R
and moment of inertia I. Determine the linear
acceleration of the masses if m1 = 5 kg, m2 = 5.1
kg, R = 0.1 m, and I = 10-3 kg m2.
Impulse momentum: AUC exam #77
Impulse momentum
In a crash test, a 1700-kg car collides with a wall.
The collision lasts 0.12 seconds, and the initial
and final speeds are 13.6 m/s and -1.3 m/s,
respectively. What is the impulse?
Ohanian (1985), ch. 10, ex. 1
Work, energy, power: bobsled run
A bobsled run at Lake Placid descends 148 m
from its highest point to its lowest point.
Suppose that a sled, initially at rest, slides with
negligible friction. What speed will the sled
attain at the lowest point?
a.
b.
c.
d.
0 m/s
21 m/s
54 m/s
148 m/s
Ohanian (1985), ch. 7, ex. 6
Work, energy, power: variable force
A spring has a spring constant of 4x104 N/m, and
it is initially relaxed. How much work must be
done to compress the spring by 0.1 m?
a.
b.
c.
d.
2J
20 J
200 J
2000 J
Work, energy, power: AUC exam #75