Upload
altammar13
View
221
Download
0
Embed Size (px)
Citation preview
8/11/2019 Dynamics Concepts
1/58
8/11/2019 Dynamics Concepts
2/58
CONCEPT QUIZ
1. The block (mass = m) is moving upward with a speed v.Draw the FBD if the kinetic friction coefficient is k.
A) B)
C) D) None of the above.mg
kmg
N
mg
N
kN
N
mg
kN
v
8/11/2019 Dynamics Concepts
3/58
CONCEPT QUIZ
(continued)
2. Packaging for oranges is tested using a machine that exertsay= 20 m/s2and ax= 3 m/s
2, simultaneously. Select the
correct FBD and kinetic diagram for this condition.
A) B)
C) D)
=
may
max
W
RyRx
= max
W
RyRx
=
may
max
W
Ry
=
may
Ry
y
x
8/11/2019 Dynamics Concepts
4/58
CHECK YOUR UNDERSTANDING QUIZ
1. If the cable has a tension of 3 N,determine the acceleration of block B.
A) 4.26 m/s2 B) 4.26 m/s2
C) 8.31 m/s2 D) 8.31 m/s2
10 kg
4 kg
k=0.4
2. Determine the acceleration of the block.
A) 2.20 m/s
2
B) 3.17 m/s
2
C) 11.0 m/s2 D) 4.26 m/s2
5 kg
60 N
30
8/11/2019 Dynamics Concepts
5/58
8/11/2019 Dynamics Concepts
6/58
ATTENTION QUIZ
1. The tangential acceleration of an object
A) represents the rate of change of the velocity vectorsdirection.
B) represents the rate of change in the magnitude of the
velocity.
C) is a function of the radius of curvature.
D) Both B and C.
2. The block has a mass of 20 kg and a speed of
v = 30 m/s at the instant it is at its lowest point.
Determine the tension in the cord at this instant.
A) 1596 N B) 1796 N
C) 1996 N D) 2196 N
10 m
v = 30m/s
8/11/2019 Dynamics Concepts
7/58
CONCEPT QUIZ
1. When a pilot flies an airplane in a
vertical loop of constant radius ratconstant speed v, his apparent weight
is maximum at
A) Point A B) Point B (top of the loop)
C) Point C D) Point D (bottom of the loop)
r A
B
C
D
8/11/2019 Dynamics Concepts
8/58
READING QUIZ
1. What is the work done by the force F?A) F s B) F s
C) Zero D) None of the above. s
s1 s2
F
2. If a particle is moved from 1 to 2, the work done on the
particle by the force, FRwill be
A) B)
C) D)
2
1
s
t
s
F ds
2
1
s
ts
F ds-
2
1
s
ns
F ds 2
1
s
ns
F ds-
8/11/2019 Dynamics Concepts
9/58
CONCEPT QUIZ
1. A spring with an un-stretched length of 5 in expands from a
length of 2 in to a length of 4 in. The work done onthe springis _________ inlb .
A) -[0.5 k(4 in)2- 0.5 k(2 in)2] B) 0.5 k (2 in)2
C) -[0.5 k(3 in)
2
- 0.5 k(1 in)
2
] D) 0.5 k(3 in)
2
- 0.5 k(1 in)
2
2. If a spring force is F = 5 s3 N/m and the spring is compressed
by s = 0.5 m, the work done on a particle attached to the
spring will be
A) 0.625 N m B) 0.625 N m
C) 0.0781 N m D) 0.0781 N m
8/11/2019 Dynamics Concepts
10/58
ATTENTION QUIZ
1. What is the work done by the normal
force N if a 10 lb box is moved from Ato B ?
A) - 1.24 lb ft B) 0 lb ft
C) 1.24 lb ft D) 2.48 lb ft
2. Two blocks are initially at rest. How many equations would
be needed to determine the velocity of block A after block B
moves 4 m horizontally on the smooth surface?
A) One B) Two
C) Three D) Four
2 kg
2 kg
8/11/2019 Dynamics Concepts
11/58
READING QUIZ
1. The formula definition of power is ___________.
A) dU / dt B) Fv
C) Fdr/dt D) All of the above.
2. Kinetic energy results from _______.
A) displacement B) velocity
C) gravity D) friction
8/11/2019 Dynamics Concepts
12/58
CONCEPT QUIZ
2. A twin engine jet aircraft is climbing at a 10 degree angle at
260 ft/s. The thrust developed by a jet engine is 1000 lb.
The power developed by the aircraft is
A) (1000 lb)(260 ft/s) B) (2000 lb)(260 ft/s) cos 10
C) (1000 lb)(260 ft/s) cos 10 D) (2000 lb)(260 ft/s)
1. A motor pulls a 10 lb block up a smoothincline at a constant velocity of 4 ft/s.
Find the power supplied by the motor.
A) 8.4 ftlb/s B) 20 ftlb/s
C) 34.6 ftlb/s D) 40 ftlb/s
30
8/11/2019 Dynamics Concepts
13/58
READING QUIZ
1. The potential energy of a spring is ________A) always negative. B) always positive.
C) positive or negative. D) equal to ks.
2. When the potential energy of a conservative system
increases, the kinetic energy _________
A) always decreases. B) always increases.
C) could decrease or D) does not change.increase.
8/11/2019 Dynamics Concepts
14/58
CONCEPT QUIZ
2. Recall that the work of a spring is U1-2 = - k(s22s1
2) and
can be either positive or negative. The potential energy of a
spring is V = ks2. Its value is __________
A) always negative. B) either positive or negative.
C) always positive. D) an imaginary number!
1. If the work done by a conservative force on a particle as itmoves between two positions is10 ftlb, the change in its
potential energy is _______
A) 0 ftlb. B) -10 ftlb.
C) +10 ftlb. D) None of the above.
8/11/2019 Dynamics Concepts
15/58
ATTENTION QUIZ
1. The principle of conservation of energy is usually ______ toapply than the principle of work & energy.
A) harder B) easier
C) the same amount of work D) It is a mystery!
2. If the pendulum is released from the
horizontal position, the velocity of its
bob in the vertical position is _____
A) 3.8 m/s. B) 6.9 m/s.
C) 14.7 m/s. D) 21 m/s.
8/11/2019 Dynamics Concepts
16/58
READING QUIZ
1. The linear impulse and momentum equation is obtained byintegrating the ______ with respect to time.
A) friction force B) equation of motion
C) kinetic energy D) potential energy
2. Which parameter is not involved in the linear impulse and
momentum equation?
A) Velocity B) Displacement
C) Time D) Force
8/11/2019 Dynamics Concepts
17/58
8/11/2019 Dynamics Concepts
18/58
READING QUIZ
1. The internal impulses acting on a system of particles
always __________A) equal the external impulses. B) sum to zero.
C) equal the impulse of weight. D) None of the above.
2. If an impulse-momentum analysis is considered during the
very short time of interaction, as shown in the picture, weight
is a/an __________
A) impulsive force.B) explosive force.
C) non-impulsive force.
D) internal force.
8/11/2019 Dynamics Concepts
19/58
CONCEPT QUIZ
2) A drill rod is used with a air hammer for making holes in
hard rock so explosives can be placed in them. How many
impulsive forces act on the drill rod during the drilling?
A) None B) One
C) Two D) Three
1) Over the short time span of a tennis ball hitting the racket
during a players serve, the balls weight can be
considered _____________
A) nonimpulsive.
B) impulsive.
C) not subject to Newtons second law.D) Both A and C.
8/11/2019 Dynamics Concepts
20/58
ATTENTION QUIZ
2. The 200-g baseball has a horizontal velocity of 30 m/s when it
is struck by the bat, B, weighing 900-g, moving at 47 m/s.
During the impact with the bat, how many impulses of
importance are used to find the final velocity of the ball?
A) Zero B) One
C) Two D) Three
1. The 20 g bullet is fired horizontally at 1200 m/s into the
300 g block resting on a smooth surface. If the bulletbecomes embedded in the block, what is the velocity of the
block immediately after impact.
A) 1125 m/s B) 80 m/s
C) 1200 m/s D) 75 m/s
1200 m/s
BAT
vball
vbat
8/11/2019 Dynamics Concepts
21/58
READING QUIZ
1. When the motion of one or both of the particles is at an angle
to the line of impact, the impact is said to be ________
A) central impact. B) oblique impact.
C) major impact. D) None of the above.
2. The ratio of the restitution impulse to the deformation
impulse is called _________
A) impulse ratio. B) restitution coefficient.
C) energy ratio. D) mechanical efficiency.
8/11/2019 Dynamics Concepts
22/58
CONCEPT QUIZ
2. Under what condition is the energy lost during a collision
maximum?
A) e= 1.0 B) e =0.0
C) e= -1.0 D) Collision is non-elastic.
1. Two balls impact with a coefficient of restitution of 0.79.
Can one of the balls leave the impact with a kinetic energygreater than before the impact?
A) Yes B) No
C) Impossible to tell D) Dont pick this one!
8/11/2019 Dynamics Concepts
23/58
ATTENTION QUIZ
2. A particle strikes the smooth surface with a
velocity of 30 m/s. If e= 0.8, (vx)2is
_____ after the collision.
A) zero B) equal to (vx)1
C) less than (vx)1 D) greater than (vx)1
v30 m/s x
y
30
1. Block B (1 kg) is moving on the smooth surface at 10 m/s
when it squarely strikes block A (3 kg), which is at rest. Ifthe velocity of block A after the collision is 4 m/s to the
right, (vB)2is
A) 2 m/s B) 7 m/s
C) 7 m/s D) 2 m/sB A
vB=10 m/s
8/11/2019 Dynamics Concepts
24/58
READING QUIZ
1. Select the correct expression for the angular momentum of a
particle about a point.
A) r v B) r (m v)
C) v r D) (m v) r
2. The sum of the moments of all external forces acting on a
particle is equal to
A) angular momentum of the particle.
B) linear momentum of the particle.
C) time rate of change of angular momentum.
D) time rate of change of linear momentum.
8/11/2019 Dynamics Concepts
25/58
8/11/2019 Dynamics Concepts
26/58
ATTENTION QUIZ
1. A ball is traveling on a smooth surface in a 3 ft radius circle
with a speed of 6 ft/s. If the attached cord is pulled down
with a constant speed of 2 ft/s, which of the followingprinciples can be applied to solve for the velocity of the ball
when r = 2 ft?
A) Conservation of energy
B) Conservation of angular momentum
C) Conservation of linear momentum
D) Conservation of mass
2. If a particle moves in the z - y plane, its angular momentumvector is in the
A) x direction. B) y direction.
C) z direction. D) z - y direction.
8/11/2019 Dynamics Concepts
27/58
8/11/2019 Dynamics Concepts
28/58
ATTENTION QUIZ
1. The fan blades suddenly experience an angular acceleration
of 2 rad/s2. If the blades are rotating with an initial angularvelocity of 4 rad/s, determine the speed of point P when the
blades have turned 2 revolutions
(when = 8.14 rad/s).
A) 14.2 ft/s B) 17.7 ft/s
C) 23.1 ft/s D) 26.7 ft/s
2. Determine the magnitude of the acceleration at P when theblades have turned the 2 revolutions.
A) 0 ft/s2 B) 3.5 ft/s2
C) 115.95 ft/s2 D) 116 ft/s2
8/11/2019 Dynamics Concepts
29/58
ATTENTION QUIZ
2. If vA=10 m/s and aA=10 m/s, determine
the angular acceleration, a,when = 30.
A) 0 rad/s2 B) -50.2 rad/s2
C) -112 rad/s2 D) -173 rad/s2
1. The sliders shown below are confined to move in the
horizontal and vertical slots. If vA=10 m/s, determine theconnecting bars angular velocity when = 30.
A) 10 rad/s B) 10 rad/s
C) 8.7 rad/s D) 8.7 rad/s
8/11/2019 Dynamics Concepts
30/58
CHECK YOUR UNDERSTANDING QUIZ
1. If the disk is moving with a velocity at point
O of 15 ft/s and = 2 rad/s, determine thevelocity at A.
A) 0 ft/s B) 4 ft/s
C) 15 ft/s D) 11 ft/s
2. If the velocity at A is zero, then determine the angular
velocity, .
A) 30 rad/s B) 0 rad/s
C) 7.5 rad/s D) 15 rad/s
2 ftV=15 ft/s
A
O
8/11/2019 Dynamics Concepts
31/58
ATTENTION QUIZ
1. Which equation could be used to find
the velocity of the center of the gear, C,if the velocity vAis known?
A) vB= vA+ gear rB/A B) vA= vC+ gear rA/C
C) vB= vC+ gear rC/B D) vA= vC+ gear rC/A
vA
2. If the bars velocity at A is 3 m/s, what
base point (first term on the RHS of the
velocity equation) would be best used to
simplify finding the bars angular
velocity when = 60?
A) A B) B
C) C D) No difference.
A
4 m
B
C
8/11/2019 Dynamics Concepts
32/58
READING QUIZ
1. If applicable, the method of instantaneous center can be used
to determine the __________ of any point on a rigid body.
A) velocity B) acceleration
C) velocity and acceleration D) force
2. The velocity of any point on a rigid body is __________ to
the relative position vector extending from the IC to the
point.
A) always parallel B) always perpendicular
C) in the opposite direction D) in the same direction
8/11/2019 Dynamics Concepts
33/58
ATTENTION QUIZ
1. The wheel shown has a radius of 15 in and rotates clockwise
at a rate of = 3 rad/s. What is vB?A) 5 in/s B) 15 in/s
C) 0 in/s D) 45 in/s
2. Point A on the rod has a velocity of 8 m/s to the right.
Where is the IC for the rod?
A) Point A.
B) Point B.C) Point C.
D) Point D.
C
D
8/11/2019 Dynamics Concepts
34/58
CONCEPT QUIZ
2. What are the tangential and normal components of the
relative acceleration of point B with respect to G.
A) - 2riarj B) - ari+ 2rj
C) 2riarj D) Zero.
1. If a ball rolls without slipping, select the
tangential and normal components ofthe relative acceleration of point A with
respect to G.
A) ari+2rj B) - ari+2rj
C) 2riarj D) Zero.
8/11/2019 Dynamics Concepts
35/58
ATTENTION QUIZ
1. Two bodies contact one another
without slipping. If the tangentialcomponent of the acceleration of point
A on gear B is 100 ft/sec2, determine
the tangential component of the
acceleration of point A on gear C.
A) 50 ft/sec2 B) 100 ft/sec2
C) 200 ft/sec2 D) None of above.
2. If the tangential component of the acceleration of point A on
gear B is 100 ft/sec2, determine the angular acceleration of
gear B.
A) 50 rad/sec2 B) 100 rad/sec2
C) 200 rad/sec2 D) None of above.
8/11/2019 Dynamics Concepts
36/58
READING QUIZ
1. Mass moment of inertia is a measure of the resistance of a
body to _____________.
A) translational motion B) deformation
C) angular acceleration D) impulsive motion
2. Mass moment of inertia is always____________.
A) a negative quantity
B) a positive quantity
C) an integer value
D) zero about an axis perpendicular to the plane of motion
8/11/2019 Dynamics Concepts
37/58
ATTENTION QUIZ
2. If the mass of body A and B are equal but kA= 2kB, then
____________.
A) IA= 2IB B) IA= (1/2)IB
C) IA= 4IB D) IA= (1/4)IB
1. The mass moment of inertia of any body about its center ofmass is always ____________.
A) maximum B) minimum
C) zero D) None of the above
8/11/2019 Dynamics Concepts
38/58
READING QUIZ
1. When a rigid body undergoes translational motion due to
external forces, the translational equations of motion (EOM)can be expressed for _____________.
A) the center of rotation B) the center of mass
C) any arbitrary point D) All of the above
2. The rotational EOM about the mass center of the rigid body
indicates that the sum of moments due to the external loads
equals _____________.A) IG a B) m aG
C) IG a + m aG D) None of the above.
8/11/2019 Dynamics Concepts
39/58
8/11/2019 Dynamics Concepts
40/58
CONCEPT QUIZ
A
B2. A 2 lb disk is attached to a uniform 6 lb
rod AB with a frictionless collar at B.If the disk rolls withslipping, select the
correct FBD.
6 lb
2 lb
Na
Nb
kNa
8 lb
Na
NbA) B) C)
6 lb
2 lb
Na
Nb
sNaFk
8/11/2019 Dynamics Concepts
41/58
READING QUIZ
1. In rotational motion, the normal component of acceleration
at the bodys center of gravity (G) is always __________.A) zero
B) tangent to the path of motion of G
C) directed from G toward the center of rotation
D) directed from the center of rotation toward G
2. If a rigid body rotates about point O, the sum of the
moments of the external forces acting on the body about
point O equals?
A) IGa B) IOa
C) m aG D) m aO
8/11/2019 Dynamics Concepts
42/58
CONCEPT QUIZ
2. In the above problem, when = 90, the horizontal
component of the reaction at pin O is __________.A) zero B) m g
C) m (l/2) 2 D) None of the above
1. If a rigid bar of length l (above) is released
from rest in the horizontal position (= 0),the magnitude of its angular acceleration is
at maximum when
A) = 0 B) = 90
C) = 180 D) = 0and 180
8/11/2019 Dynamics Concepts
43/58
1. A drum of mass m is set into motion in two ways: (a) by a
constant 40 N force, and, (b) by a block of weight 40 N. If aa
and abrepresent the angular acceleration of the drum in each
case, select the true statement.
A) aa> ab B) aa< ab
C) aa= ab D) None of the above
2. In case (b) above, what is the tension T in the cable?
A) T = 40 N B) T < 40 N
C) T > 40 N D) None of the above
ATTENTION QUIZ(a) (b)m m
T
10 lb 10 lb
8/11/2019 Dynamics Concepts
44/58
READING QUIZ
1. If a disk rolls on a rough surface without slipping, the
acceleration af the center of gravity (G) will _________ andthe friction force will be __________.
A) not be equal to a r; less thansN
B) be equal to a r;equal tokN
C) be equal to a r; less than sN
D) None of the above
2. If a rigid body experiences general plane motion, the sum of
the moments of external forces acting on the body about anypoint P is equal to __________.
A) IP B) IP + maP
C) m aG D) IG +rGP maP
8/11/2019 Dynamics Concepts
45/58
CONCEPT QUIZ
2. For the situation above, the moment equation about G is?
A) 0.75 (FfA) - 0.2(30) = - (80)(0.32)a
B) -0.2(30) = - (80)(0.32)a
C) 0.75 (FfA) - 0.2(30) = - (80)(0.32)a+ 80aG
D) None of the above
1. An 80 kg spool (kG= 0.3 m) is on a
rough surface and a cable exerts a 30 Nload to the right. The friction force at A
acts to the __________ and the aGshould be directed to the __________ .
A) right, left B) left, rightC) right, right D) left, left
30N
A
0.2m
0.75m
a
G
8/11/2019 Dynamics Concepts
46/58
ATTENTION QUIZ
2. Select the equation that best represents the no-slip
assumption.
A) Ff= sN B) Ff= kN
C) aG = r a D) None of the above
1. A slender 100 kg beam is suspended by a
cable. The moment equation about point A is?
A) 3(10) = 1/12(100)(42) a
B) 3(10) = 1/3(100)(42) a
C) 3(10) = 1/12(100)(42
) a+ (100 aGx)(2)D) None of the above
4m
10 N
3m
A
8/11/2019 Dynamics Concepts
47/58
READING QUIZ
1. Kinetic energy due to rotation of the body is defined as
A) (1/2) m (vG)2. B) (1/2) m (vG)
2 + (1/2) IG 2.
C) (1/2) IG 2. D) IG
2.
2. When calculating work done by forces, the work of aninternal force does not have to be considered because
____________.
A) internal forces do not exist
B) the forces act in equal but opposite collinear pairs
C) the body is at rest initially
D) the body can deform
8/11/2019 Dynamics Concepts
48/58
CONCEPT QUIZ
1. If a rigid body rotates about its center of gravity, its
translational kinetic energy is ___________ at all times.
A) constant
B) zero
C) equal to its rotational kinetic energy
D) Cannot be determined
m
L
2. A rigid bar of mass m and length L is released from rest in
the horizontal position. What is the rods angular velocity
when it has rotated through 90?
A) g/3L B) 3g/L
C) 12g/L D) g/L
8/11/2019 Dynamics Concepts
49/58
ATTENTION QUIZ
1. A disk and a sphere, each of mass m and radius r, are
released from rest. After 2 full turns, which body has alarger angular velocity? Assume roll without slip.
A) Sphere B) Disk
C) The two are equal. D) Cannot be determined.
r
2. A slender bar of mass m and length L is released from rest in
a horizontal position. The work done by its weight when it
has rotated through 90is?A) m g (p/2) B) m g L
C) m g (L/2) D) -m g (L/2)
m
L
8/11/2019 Dynamics Concepts
50/58
READING QUIZ
1. Elastic potential energy is defined as ___________.
A) + (1/2) k (s)2 B) - (1/2) k (s)2
C) + (1/2) k (v)2 D) None of the above
2. The kinetic energy of a rigid body consists of the
kinetic energy due to ___________.
A) translational motion and rotational motion
B) only rotational motionC) only translational motion
D) the deformation of the body
8/11/2019 Dynamics Concepts
51/58
8/11/2019 Dynamics Concepts
52/58
ATTENTION QUIZ
1. Blocks A and B are released from rest and the
disk turns 2 revolutions. The V2of the systemincludes a term for ______________.
A) only the 40 kg block
B) only the 80 kg block
C) the disk and both blocksD) only the two blocks
1m
40 kg
80 kg
datum
2. A slender bar is released from rest while in the horizontal
position. The kinetic energy (T2) of the bar when it has
rotated through 90is?
A) m (vG2)2 B) IG (2)
2
C) k (s1)2- W (L/2) D) m (vG2)
2 + IG (2)2
m
L
8/11/2019 Dynamics Concepts
53/58
READING QUIZ
1. The angular momentum of a rotating two-dimensional rigid
body about its center of mass G is ___________.
A) m vG B) IG vG
C) m D) IG
2. If a rigid body rotates about a fixed axis passing through its
center of mass, the bodys linear momentum is __________.
A) a constant B) zero
C) m vG D) IG
8/11/2019 Dynamics Concepts
54/58
8/11/2019 Dynamics Concepts
55/58
8/11/2019 Dynamics Concepts
56/58
8/11/2019 Dynamics Concepts
57/58
CONCEPT QUIZ
2. For the rod in question 1, the angular momentum about A of
the rod and bullet just after impact will be ___________.
A) m vb + M(0.5)2 B) m(0.5)22+ M(0.5)22
C) m(0.5)22+ M(0.5)22 D) zero
+ (1/12) M 2
1. A slender rod (mass = M) is at rest. If abullet(mass = m) is
fired with a velocity of vb, the angular
momentum of the bullet about A just
before impact is ___________.
A) 0.5 m vb2 B) m vb
C) 0.5 m vb D) zero
G
1.0
A20.5
m
8/11/2019 Dynamics Concepts
58/58