Dynamics Concepts

8/11/2019 Dynamics Concepts

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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


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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


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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


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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


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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


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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-


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


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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


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


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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


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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.


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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.


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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.


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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


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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.


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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.


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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


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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.


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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!


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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


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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.


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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.


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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


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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


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


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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


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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


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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


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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.


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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.


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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


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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


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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.


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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Dynamics Concepts

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