##### choi (tc29389) - Phys1 6SW6Wk5 0517b - sabapathy - (6896-(Answered)

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**Question**

I need help on question #17 please:

Three strings (labeled A, B, and C) attached

to the sides of a square box are tied together

by a knot as shown in the figure. The tension

in the string labeled C is 64 N.

Calculate the magnitude of the tension in

the string marked A.

choi (tc29389) ? Phys1 6SW6Wk5 0517b ? sabapathy ? (6896 1)

1

This print-out should have 20 questions.

Multiple-choice questions may continue on

the next column or page ? find all choices

before answering.

R

?

001 10.0 points

A bowling ball has a mass of 4.7 kg, a moment

of inertia of 0.067868 kg ? m2 , and a radius of

0.19 m. It rolls along the lane without slipping

at a linear speed of 3.9 m/s.

What is the total kinetic energy of the

rolling ball?

Answer in units of J.

I

T1

T2

m1

?

m2

003 (part 1 of 2) 10.0 points

A dentist?s drill starts from rest. After 3.87 s

of constant angular acceleration, it turns at a

rate of 25700 rev/min.

Find the drill?s angular acceleration.

Answer in units of rad/s2 .

004 (part 2 of 2) 10.0 points

Find the angle through which the drill rotates

during this period.

Answer in units of rad.

005 (part 1 of 2) 10.0 points

An Atwood machine is constructed using a

disk of moment of inertia I. The masses are

m1 and m2 with m1 > m2 .

m2 g

m2

m1 g

a

m1

a

T1

002 10.0 points

The center of mass of a pitched baseball or

radius 1.92 cm moves at 49.7 m/s. The ball

spins about an axis through its center of mass

with an angular speed of 51.4 rad/s.

Calculate the ratio of the rotational energy

to the translational kinetic energy. Treat the

ball as a uniform sphere.

T2

Consider the free body diagrams

and the following set of equations, where all

variables are positive.

I: m1 g ? T1 = m1 a

J : T1 ? m1 g = m1 a

K: T1 = m1 a

X : m2 g ? T2 = m2 a

Y: T2 ? m2 g = m2 a

Z: T2 = m2 a

a

R

a

B: (T1 ? T2 ) R = I

R

C: (T2 ? T1 ) R = I a

D: (T1 ? T2 ) R = I a Choose the correct

set of equations of motion.

A: (T2 ? T1 ) R = I

1. K,

Z,

and

C

2. I,

X , and

B

3. K,

Z,

and

A

4. J ,

Y, and

B

5. J ,

Y, and

A

choi (tc29389) ? Phys1 6SW6Wk5 0517b ? sabapathy ? (6896 1)

6. I,

X , and

A

7. I,

X , and

D

2

ABCDE F G

10 20 30 40 50 60

8. I,

X , and

C

9. K,

Z, and

B

10. I,

Y, and

B

006 (part 2 of 2) 10.0 points

Let the mass on the left be 7.39 kg, the

mass on the right 4.99 kg, the acceleration

1.34889 m/s2 and the radius of the pulley

0.1 m.

Determine the magnitude of the torque exerted on the pulley. The acceleration of gravity is 9.8 m/s2 .

Answer in units of N ? m.

007 10.0 points

Three forces act on an object.

If the object is in translational equilibrium,

which of the following must be true?

I. The vector sum of the three forces must

equal zero;

II. The magnitude of the three forces must

be equal;

III. The three forces must be parallel.

1. II only

21 kg

28 kg

If the mass of the stick is negligible, at

which of the points indicated should a cord be

attached if the stick is to remain horizontal

when suspended from the cord?

1. D

2. A

3. F

4. B

5. E

6. C

7. G

009 (part 1 of 2) 10.0 points

Consider the 650 N weight held by two cables

shown below. The left-hand cable had tension

T and makes an angle of ? with the wall. The

right-hand cable had tension 800 N and makes

an angle of 33? with the ceiling.

2. II and III only

3. I only

4. I, II and III

5. I and III only

008 10.0 points

Two objects of masses 21 kg and 28 kg are

hung from the ends of a stick that is 70 cm

long and has marks every 10 cm, as shown.

T

?

33

80

0N

?

650 N

a) What is the tension T in the left-hand

cable slanted at an angle of ? with respect to

the wall?

Answer in units of N.

010 (part 2 of 2) 10.0 points

b) What is the angle ? which the left-hand

cable makes with respect to the wall?

choi (tc29389) ? Phys1 6SW6Wk5 0517b ? sabapathy ? (6896 1)

Answer in units of ? .

011 10.0 points

A wheel rotating with a constant angular acceleration turns through 10 revolutions during

a 5 s time interval. Its angular velocity at the

end of this interval is 18 rad/s.

What is the angular acceleration of the

wheel? Note that the initial angular velocity is not zero.

Answer in units of rad/s2 .

012 (part 1 of 3) 10.0 points

A string is wound around a uniform disc

whose mass is 2.7 kg and radius is 0.29 m ,

see figure below. The disc is released from

rest with the string vertical and its top end

tied to a fixed support.

The acceleration of gravity is 9.8 m/s2 .

h

0.29 m

?

2.7 kg

As the disc descends, calculate the tension

in the string.

Answer in units of N.

013 (part 2 of 3) 10.0 points

Calculate the magnitude of the acceleration

of its center of mass.

015 10.0 points

A 96 N block rests on a table. The suspended mass has a weight of 32 N.

96 N

?s

32 N

What frictional force is required to keep the

blocks from moving?

Answer in units of N.

016 10.0 points

A rotating wheel requires 4 s to rotate through

19.3 rev. Its angular speed at the end of the

4 s interval is 119.7 rad/s.

What is its constant angular acceleration?

Assume the angular acceleration has the same

sign as the angular velocity.

Answer in units of rad/s2 .

017 10.0 points

Three strings (labeled A, B, and C) attached

to the sides of a square box are tied together

by a knot as shown in the figure. The tension

in the string labeled C is 64 N.

Three Strings Knotted Together

10

9

1. acm = 6.53333 m/s2

3. acm = 5.684 m/s2

4. acm = 5.94533 m/s2

014 (part 3 of 3) 10.0 points

After starting from rest, calculate the speed

of its center of mass when the center of mass

has fallen ?h = 2.7 m.

Answer in units of m/s.

8

y Distance (m)

2. acm = 7.252 m/s2

3

B

7

TB

6

5

C

4

64 N

A

3

2

TA

1

0

0

1

2

3 4 5 6 7

x Distance (m)

8

9 10

choi (tc29389) ? Phys1 6SW6Wk5 0517b ? sabapathy ? (6896 1)

Figure: Drawn to scale.

Calculate the magnitude of the tension in

the string marked A.

Answer in units of N. Your answer must

be within ? 3.0%

018 10.0 points

At t = 0, a wheel rotating about a fixed axis at

a constant angular deceleration of 0.8 rad/s2

has an angular velocity of 2.2 rad/s and an

angular position of 9.2 rad.

What is the angular position of the wheel

after 2 s?

Answer in units of rad.

F

6. 9

?

N

019 (part 1 of 2) 10.0 points

The 9.5 N weight is in equilibrium under the

influence of the three forces acting on it. The

F force acts from above on the left at an angle

of ? with the horizontal. The 6.9 N force acts

from above on the right at an angle of 64? with

the horizontal. The force 9.5 N acts straight

down.

?

64

9.5 N

What is the magnitude of the force F ?

Answer in units of N.

020 (part 2 of 2) 10.0 points

What is the angle ? of the force F as shown

in the figure?

Answer in units of ? .

4

Paper#9255680 | Written in 27-Jul-2016

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