### Surface Tension – Physics chapters 2 Quiz

The key terms of Physics Chapter 2 Quiz include, Surface tension, Moment of inertia, Density, Solid sphere, total kinetic energy, spherical particles, unit of viscosity, Reynolds number, angular acceleration, centipoise, angular speed.

Water is being sprayed from a nozzle at the end of a garden hose of diameter 2.0 cm. If the

nozzle has an opening of diameter 0.50 cm, and if the water leaves the nozzle

at a speed of 10 m/s, what is the speed of the water inside the hose?**a. 0.63 m/s – correct**

b. 0.80 m/s

c. 2.5 m/s

d. also 10 m/s

A unit for viscosity, the centipoise, is equal to which of the following?**a. 10-3 N·s/m2** **– correct**

b. 10-2 N·s/m2

c. 10-1 N·s/m2

d. 102

N·s/m2

The condition for onset of turbulent flow is that the Reynolds Number

reaches what value?

a. 1 000

b. 2 000**c. 3 000 – correct**

d. 4 000

A fluid has a density of 1 040 kg/m3. If it rises to a height of 1.8 cm in a 1.0-mm diameter

capillary tube, what is the surface tension of the liquid? Assume a contact angle of zero.**a. 0.046 N/m** **– correct**

b. 0.056 N/m

c. 0.092 N/m

A pipe carrying water has a radius of 1.0 cm. If the flow velocity is 9.0

cm/s, which of the

following characterizes the flow? Take the viscosity of water to be 1.0 × 10-3

N·s/m.**a. streamlined** **– correct**

b. unstable

c. turbulent

d. stagnant

In order to overcome a surface tension of a fluid, a force of 1.32 × 10-2 N is required to lift a

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

A pipe of diameter three cm is replaced by one of the same length but of diameter six cm. If

the pressure difference between the ends of the pipe remains the same, by what

factor is the rate of flow of a viscous liquid through it changed?

a. 2

b. 4

c. 8**d. 16** **– correct**

Spherical particles of density 2.0 g/cm3

are shaken in a container of water (viscosity = 1.0 ×

10-3 N·s/m3). The water is 8.0 cm deep and is allowed to stand for 30 minutes. What is the

greatest terminal velocity of the particles still in suspension at that time?

a. 0.55 × 10-5 m/s

b 1.1 × 10-5 m/s

c. 2.2 × 10-5 m/s**d. 4.4 × 10-5 m/s** **– correct**

Spherical particles of density 2.0 g/cm3 are shaken in a container of water (viscosity = 1.0 ×

10-3 N·s/m3). The water is 8.0 cm deep and is allowed to stand for 30 minutes. What is the

radius of the largest particles still in suspension at that time?**a. 4.5 × 10-6 m** **– correct**

b. 9.0 × 10-6 m

c. 2.3 × 10-6 m

d. 5.6 × 10-6 m

A centrifuge rotates at 100 rev/s (i.e., 628 rad/s). If the test tube places

the suspension at 8.0

cm from the axis of rotation, by what factor are the terminal speeds of the

settling particles

increased as compared to sedimentation cause by gravity?**a. 3.2 × 102** **– correct**

b. 64

c. 800

d. 3.9 × 105

78. Which of the following characterizes the net force on a particle falling

through a fluid at its

terminal speed?

a. It is at a maximum.

b. It is upwards.

c. It is downwards.**d. It is zero.** **– correct**

A vault is opened by applying a force of 300 N perpendicular to the plane of

the door, 0.80 m

from the hinges. Find the torque due to this force about an axis through the

hinges.

a. 120 N⋅m**b. 240 N⋅m** **– correct**

c. 300 N⋅m

d. 360 N⋅m

A 3.0-m rod is pivoted about its left

end. A force of 6.0 N is applied perpendicular to the rod

at a distance of 1.2 m from the pivot causing a ccw torque, and a force of 5.2

N is applied at

the end of the rod 3.0 m from the pivot. The 5.2 N is at an angle of 30o

to the rod and causes a

cw torque. What is the net torque about the pivot?

a. 15 N·m

b. 0 N·m

c. -6.3 N·m**d. -0.6 N·m** **– correct**

A rod of length L is pivoted about its left end and has a force F applied

perpendicular to the

other end. The force F is now removed and another force F’ is applied at the

midpoint of the

rod. If F’ is at an angle of 30°

with respect to the rod, what is its magnitude if the resulting

torque is the same as when F was applied?

a. F

b. 2F

c. 3F**d. 4F** **– correct**

Two children seat themselves on a

seesaw. The one on the left has a weight of 400 N while

the one on the right weighs 300 N. The fulcrum is at the midpoint of the

seesaw. If the child

on the left is not at the end but is 1.50 m from the fulcrum and the seesaw is

balanced, what is

the torque provided by the weight of the child on the right?

a. 600 N·m

b. 450 N·m**c. -600 N·m** **– correct**

d. -450 N·m

A bucket filled with water has a mass of 23 kg and is attached to a rope,

which in turn, is wound around a 0.050-m radius cylinder at the top of a well. What torque does

the weight of water and bucket produce on the cylinder if the cylinder is not permitted to rotate? (g = 9.8m/s2)

a. 34 N⋅m

b. 17 N⋅m**c. 11 N⋅m** **– correct**

d. 23 N⋅m

A bucket of water with total mass 23 kg is attached to a rope, which in turn, is wound around

a 0.050-m radius cylinder at the top of a well. A crank with a turning radius of 0.25 m is

attached to the end of the cylinder. What minimum force directed perpendicular to the crank

handle is required to just raise the bucket? (Assume the rope’s mass is negligible, that

cylinder turns on frictionless bearings, and that g = 9.8 m/s2.)**a. 45 N** **– correct**

b. 68 N

c. 90 N

d. 135 N

A uniform bridge span weighs 50.0 × 103

N and is 40.0 m long. An automobile weighing

15.0 × 103

N is parked with its center of gravity located 12.0 m from the right pier. What

upward support force does the left pier provide?**a. 29.5 × 103 N** **– correct**

b. 35.5 × 103

N

c. 65.0 × 103 N

d. 32.5 × 103

N

Masses are distributed in the x,y-plane as follows: 6.0 kg at (0.0, 0.0) m,

4.0 kg at (2.0, 0.0)

m, and 5.0 kg at (2.0, 3.0) m. What is the x-coordinate of the center of

gravity of this system

of masses?

a. 18 m

b. 2.0 m**c. 1.2 m** **– correct**

d. 1.0 m

Masses are distributed in the

xy-plane as follows: 10 kg at (2.0, 6.0) m, 4.0 kg at (2.0, 0.0) m,

and 6.0 kg at (0.0, 3.0) m. Where would a 20-kg mass need to be positioned so

that the center

of gravity of the resulting four mass system would be at the origin?

a. (1.4, 3.9) m

b. (3.9, 1.4) m**c. (-1.4, -3.9) m** **– correct**

d. (-3.9, -1.4) m

A hoop of radius 1.0 m is placed in the first quadrant of an xy-coordinate

system with its rim

touching both the x-axis and the y-axis. What are the coordinates of its center

of gravity?**a. (1.0, 1.0) m** **– correct**

b. (0.7, 0.7) m

c. (0.5, 0.5) m

d. Since there is nothing at the center of the hoop, it has no center of

gravity.

. Tasha has mass 20 kg and wants to use a 4.0-m board of mass 10 kg as a

seesaw. Her friends

are busy, so Tasha seesaws by herself by putting the support at the system’s

center of gravity

when she sits on one end of the board. How far is she from the support point?

a. 2.0 m

b. 1.0 m**c. 0.67 m** **– correct**

d. 0.33 m

In order to overcome a surface tension of a fluid, a force of 1.32 × 10-2 N is required to lift a

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

An 80-kg man is one fourth of the way up a 10-m ladder that is resting

against a smooth,

frictionless wall. If the ladder has a mass of 20 kg and it makes an angle of

60° with the

ground, find the force of friction of the ground on the foot of the ladder.

a. 7.8 x 102

N

b. 2.0 x 102

N

c. 50 N**d. 1.7 x 102 N** **– correct**

A 100-N uniform ladder, 8.0 m long, rests against a smooth vertical wall.

The coefficient of

static friction between ladder and floor is 0.40. What minimum angle can the

ladder make

with the floor before it slips?

a. 22°**b. 51°** **– correct**

c. 18°

d. 42°

4. A meter stick is supported by a knife-edge at the 50-cm mark. Doug hangs

masses of 0.40

and 0.60 kg from the 20-cm and 80-cm marks, respectively. Where should Doug

hang a third

mass of 0.30 kg to keep the stick balanced?

a. 20 cm

b. 70 cm**c. 30 cm** **– correct**

d. 25 cm

An 800-N billboard worker stands on a 4.0-m scaffold supported by vertical

ropes at each

end. If the scaffold weighs 500 N and the worker stands 1.0 m from one end,

what is the

tension in the rope nearest the worker?

a. 450 N

b. 500 N

c. 800 N**d. 850 N** **– correct**

An 800-N billboard worker stands on a

4.0-m scaffold weighing 500 N and supported by

vertical ropes at each end. How far would the worker stand from one of the

supporting ropes

to produce a tension of 550 N in that rope?

a. 1.4 m

b. 2.0 m**c. 2.5 m** **– correct**

d. 2.7 m

. A woman who weighs 500 N stands on an 8.0-m-long board that weighs 100 N.

The board is

supported at each end. The support force at the right end is 3 times the

support force at the

left end. How far from the right end is the woman standing?

a. 4.0 m

b. 2.0 m

c. 2.7 m**d. 1.6 m** **– correct**

A uniform, horizontal beam of length 6.0 m and weight 120 N is attached at

one end to a wall

by a pin connection (so that it may rotate). A cable attached to the wall above

the pin

supports the opposite end. The cable makes an angle of 60° with the horizontal.

What is the

tension in the cable needed to maintain the beam in equilibrium?

a. 35 N**b. 69 N** **– correct**

c. 60 N

d. 120 N

A uniform 1.0-N meter stick is

suspended horizontally by vertical strings attached at each

end. A 2.0-N weight is suspended from the 10-cm position on the stick, another

2.0-N weight

is suspended from the 50 cm position, and a 3.0-N weight is suspended from the

60 cm

position. What is the tension in the string attached at the 100-cm end of the

stick?

a. 1.9 N

b. 3.0 N**c. 3.5 N** **– correct**

d. 4.0 N

The quantity “moment of

inertia” (in terms of the fundamental quantities of mass, length, and

time) is equivalent to:

a. ML2

T−2

.

b. ML.**c. ML2** **– correct**

.

d. ML−1

T−2

.

. A 4.2-kg mass is placed at (3.0, 4.0) m. Where can an 8.4-kg mass be

placed so that the

moment of inertia about the z-axis is zero?

a. (-3.0, -4.0) m

b. (-6.0, -8.0) m

c. (-1.5, -2.0) m**d. There is no position giving this result.** **– correct**

A 4.0-kg mass is placed at (3.0, 4.0) m, and a 6.0-kg mass is placed at

(3.0, -4.0) m. What is

the moment of inertia of this system of masses about the x-axis?**a. 160 kg·m2** **– correct**

b. 90 kg·m2

c. 250 kg·m2

d. 32 kg·m2

A 4.0-kg mass is placed at (3.0, 4.0) m, and a 6.0-kg mass is placed at

(3.0, -4.0) m. What is

the moment of inertia of this system of masses about the y-axis?

a. 160 kg·m2**b. 90 kg·m2** **– correct**

c. 250 kg·m2

d. 180 kg·m2

In order to overcome a surface tension of a fluid, a force of 1.32 × 10-2 N is required to lift a

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

A 4.0-kg mass is placed at (3.0, 4.0)

m, and a 6.0-kg mass is placed at (3.0, -4.0) m. What is

the moment of inertia of this system of masses about the z-axis?

a. 160 kg·m2

b. 90 kg·m2**c. 250kg·m2** **– correct**

d. 180 kg·m2

If a net torque is applied to an object, that object will experience:

a. a constant angular speed.**b. an angular acceleration.** **– correct**

c. a constant moment of inertia.

d. an increasing moment of inertia.

According to Newton’s second law, the

angular acceleration experienced by an object is

directly proportional to:

a. its moment of inertia.**b. the net applied torque**. **– correct**

c. the object’s size.

d. choices a and b above are both valid.

A ventilation fan with a moment of

inertia of 0.034 kg⋅m2

has a net torque of 0.11 N⋅m

applied to it. What angular acceleration does it experience?

a. 5.3 rad/s2

b. 4.0 rad/s2**c. 3.2 rad/s2** **– correct**

d. 0.31 rad/s2

A disk has a moment of inertia of 3.0

× 10−4

kg⋅m2

and rotates with an angular speed of 3.5

rad/sec. What net torque must be applied to bring it to rest within 3 s?

a. 4.5 × 10−3 N⋅m

b. 7.5 × 10−4 N⋅m**c. 3.5 × 10−4 N⋅m** **– correct**

d. 5.0 × 10−4 N⋅m

The Earth moves about the Sun in an

elliptical orbit. As the Earth moves closer to the Sun,

which of the following best describes the Earth-Sun system’s moment of inertia?**a. decreases** **– correct**

b. increases

c. remains constant

d. none of the above choices are valid

A bowling ball has a mass of 7.0 kg, a moment of inertia of 2.8 × 10−2

kg⋅m2

and a radius of

0.10 m. If it rolls down the lane without slipping at a linear speed of 4.0

m/s, what is its

angular speed?

a. 0.80 rad/s

b. 10 rad/s

c. 0.050 rad/s**d. 40 rad/s** **– correct**

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

A baseball pitcher, loosening up his arm before a game, tosses a 0.15-kg

ball using only the

rotation of his forearm, 0.32 m in length, to accelerate the ball. If the ball

starts at rest and is

released with a speed of 12 m/s in a time of 0.40 s, what is the average

angular acceleration of

the arm and ball?

a. 0.067 rad/s2**b. 94 rad/s2** **– correct**

c. 15 rad/s2

d. 37 rad/s2

A baseball pitcher loosens up his pitching arm. He tosses a 0.15-kg ball

using only the

rotation of his forearm, 0.32 m in length, to accelerate the ball. What is the

moment of inertia

of the ball alone as it moves in a circular arc with a radius of 0.32 m?**a. 1.5 × 10−2 kg⋅m2** **– correct**

b. 16 × 10−2 kg⋅m2

c. 4.0 × 10−2 kg⋅m2

d. 7.6 × 10−2 kg⋅m2

A baseball pitcher loosens up his pitching arm. He tosses a 0.15-kg ball

using only the

rotation of his forearm, 0.32 m in length, to accelerate the ball. If the ball

starts at rest and is

released with a speed of 12 m/s in a time of 0.40 s, what torque is applied to

the ball while

being held by the pitcher’s hand to produce the angular acceleration?

a. 1.1 N⋅m

b. 11 N⋅m

c. 7.2 N⋅m**d. 1.4 N⋅m** **– correct**

A bucket of water with total mass 23 kg is attached to a rope, which in turn

is wound around

a 0.050-m radius cylinder at the top of a well. A crank with a turning radius

of 0.25 m is

attached to the end of the cylinder and the moment of inertia of cylinder and

crank is 0.12

kg⋅m2

. If the bucket is raised to the top of the well and released, what is the

acceleration of

the bucket as it falls toward the bottom of the well? (Assume rope’s mass is

negligible, that

cylinder turns on frictionless bearings and that g = 9.8 m/s2

.)**a. 3.2 m/s2** **– correct**

b. 6.3 m/s2

c. 7.4 m/s2

d. 9.8 m/s2

A bucket of water with total mass 23

kg is attached to a rope, which in turn is wound around

a 0.050-m radius cylinder at the top of a well. The bucket is raised to the top

of the well and

released. The bucket is moving with a speed of 8.0 m/s upon hitting the water

surface in the

well. What is the angular speed of the cylinder at this instant?

a. 39 rad/s

b. 79 rad/s

c. 120 rad/s**d. 160 rad/s** **– correct**

A majorette takes two batons and fastens them together in the middle at

right angles to make

an “x” shape. Each baton was 0.80 m long and each ball on the end is

0.20 kg. (Ignore the

mass of the rods.) What is the moment of inertia if the arrangement is spun

around an axis

formed by one of the batons?

a. 0.048 kg⋅m2**b. 0.064 kg⋅m2** **– correct**

c. 0.19 kg⋅m2

d. 0.32 kg⋅m2

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

A majorette takes two batons and fastens them together in the middle at

right angles to make

an “x” shape. Each baton was 0.80 m long and each ball on the end is

0.20 kg. (Ignore the

mass of the rods.) What is the moment of inertia if the arrangement is spun

around an axis

through the center perpendicular to both rods?

a. 0.064 kg⋅m2

b. 0.096 kg⋅m2**c. 0.13 kg⋅m2** **– correct**

d. 0.32 kg⋅m

A solid cylinder (I = MR2

/2) has a string wrapped around it many times. When I release the

cylinder, holding on to the string, the cylinder falls and spins as the string

unwinds. What is

the downward acceleration of the cylinder as it falls?

a. 0

b. 4.9 m/s2**c. 6.5 m/s2** **– correct**

d. 9.8 m/s2

A 40-kg boy is standing on the edge of a stationary 30-kg platform that is

free to rotate. The

boy tries to walk around the platform in a counterclockwise direction. As he

does:

a. the platform doesn’t rotate.

b. the platform rotates in a clockwise direction just fast enough so that the

boy remains

stationary relative to the ground.**c. the platform rotates in a clockwise ofdirection while the boy goes around in acounterclockwise direction relative to the ground.**

**– correct**

d. both go around with equal angular velocities but in opposite directions.

A rod of length L is hinged at one end. The moment of inertia as the rod

rotates around that

hinge is ML2

/3. Suppose a 2.00-m rod with a mass of 3.00 kg is hinged at one end and is

held

in a horizontal position. The rod is released as the free end is allowed to

fall. What is the

angular acceleration as it is released?

a. 3.70 rad/s2

**b. 7.35 rad/s2** **– correct**

c. 2.45 rad/s2

d. 4.90 rad/s2

Two hoops or rings (I = MR2

) are centered, lying on a turntable. The smaller ring has radius =

0.050 m; the larger has radius = 0.10 m. Both have a mass of 3.0 kg. What is

the total

moment of inertia as the turntable spins? Ignore the mass of the turntable.

a. 0.030 kg⋅m2

b. 0.007 5 kg⋅m2**c. 0.038 kg⋅m2** **– correct**

d. 0.075 kg⋅m2

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

An automobile accelerates from zero to 30 m/s in 6.0 s. The wheels have a

diameter of 0.40

m. What is the average angular acceleration of each wheel?

a. 5.0 rad/s2

b. 15 rad/s2**c. 25 rad/s2** **– correct**

d. 35 rad/s2

An object consists of a rod (of

length 3.0 m and negligible moment of inertia) to which four

small 2.0-kg masses are attached, one at each end and one at each point on the

rod 1.0 m from

each end. (The masses are one meter apart.) The moment of inertia of this

object about an

axis perpendicular to the rod and through one of the inner masses:

a. is 72 kg⋅m2

.**b. is 12 kg⋅m2** **– correct**

.

c. is 4 kg⋅m2

.

d. cannot be uniquely determined until it is stated which inner mass the axis

goes through.

A ventilation fan with a moment of inertia of 0.034 kg⋅m2

has a net torque of 0.11 N⋅m

applied to it. If it starts from rest, what kinetic energy will it have 8.0 s

later?

a. 31 J

b. 17 J**c. 11 J** **– correct**

d. 6.6 J

45. The total kinetic energy of a baseball thrown with a spinning motion is

a function of:

a. its linear speed but not rotational speed.

b. its rotational speed but not linear speed.**c. both linear and rotational speeds.** **– correct**

d. neither linear nor rotational speed.

A bowling ball has a mass of 7.0 kg, a moment of inertia of 2.8 × 10−2

kg⋅m2

and a radius of

0.10 m. If it rolls down the lane without slipping at a linear speed of 4.0

m/s, what is its total

kinetic energy?

a. 45 J

b. 32 J

c. 11 J**d. 78 J** **– correct**

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

A bucket of water with total mass 23

kg is attached to a rope, which in turn is wound around

a 0.050-m radius cylinder, with crank, at the top of a well. The moment of

inertia of the

cylinder and crank is 0.12 kg⋅m2

. The bucket is raised to the top of the well and released to

fall back into the well. What is the kinetic energy of the cylinder and crank

at the instant the

bucket is moving with a speed of 8.0 m/s?

a. 2.1 × 103 J**b. 1.5 × 103 J** **– correct**

c. 0.70 × 103 J

d. 0.40 × 103 J

A solid sphere of mass 4.0 kg and radius 0.12 m is at rest at the top of a

ramp inclined 15°. It

rolls to the bottom without slipping. The upper end of the ramp is 1.2 m higher

than the lower

end. Find the sphere’s total kinetic energy when it reaches the bottom.

a. 70 J**b. 47 J** **– correct**

c. 18 J

d. 8.8 J

A solid sphere of mass 4.0 kg and radius 0.12 m starts from rest at the top

of a ramp inclined

15°, and rolls to the bottom. The upper end of the ramp is 1.2 m higher than

the lower end.

What is the linear speed of the sphere when it reaches the bottom of the ramp?

(Note: I = 0.4MR2 for a solid sphere and g = 9.8 m/s2)

a. 4.7 m/s**b. 4.1 m/s** **– correct**

c. 3.4 m/s

d. 2.4 m/s

. A solid cylinder of mass 3.0 kg and radius 0.2 m starts from rest at the

top of a ramp, inclined

15°, and rolls to the bottom without slipping. (For a cylinder I = 0.5MR2

) The upper end of

the ramp is 1.2 m higher than the lower end. Find the linear speed of the

cylinder when it

reaches the bottom of the ramp. (g = 9.8 m/s2)

a. 4.7 m/s

b. 4.3 m/s**c. 4.0 m/s** **– correct**

d. 2.4 m/s

A gyroscope has a moment of inertia of 0.14 kg⋅m2

and an initial angular speed of 15 rad/s.

Friction in the bearings causes its speed to reduce to zero in 30 s. What is

the value of the

average frictional torque?

a. 3.3 × 10−2 N⋅m

b. 8.1 × 10−2 N⋅m

c. 14 × 10−2 N⋅m**d. 7.0 × 10−2 N⋅m** **– correct**

A gyroscope has a moment of inertia of 0.140 kg⋅m2 and has

an initial angular speed of 15.0

rad/s. If a lubricant is applied to the bearings of the gyroscope so that

frictional torque is

reduced to 2.00 × 10−2

N⋅m,

then in what time interval will the gyroscope coast from 15.0

rad/s to zero?

a. 150 s**b. 105 s** **– correct**

c. 90.0 s

d. 180 s

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

.A cylinder with its mass concentrated toward the center has a moment of

inertia of 0.1 MR2

.

If this cylinder is rolling without slipping along a level surface with a

linear speed v, what is

the ratio of its rotational kinetic energy to its linear kinetic energy?**a. 1/l0** **– correct**

b. 1/5

c. 1/2

d. 1/1

A solid sphere with mass, M, and radius, R, rolls along a level surface

without slipping with a

linear speed, v. What is the ratio of rotational to linear kinetic energy? (For

a solid sphere, I = 0.4 MR2).

a. 1/4

b. 1/2

c. 1/1**d. 2/5** **– correct**

A rotating flywheel can be used as a method to store energy. If it is

required that such a

device be able to store up to a maximum of 1.00 × 106

J when rotating at 400 rad/s, what

moment of inertia is required?

a. 50 kg⋅m2

b. 25 kg⋅m2**c. 12.5 kg⋅m2** **– correct**

d. 6.3 kg⋅m2

A rotating flywheel can be used as a

method to store energy. If it has 1.0 × 106

J of kinetic

energy when rotating at 400 rad/s, and if a frictional torque of 4.0 N⋅m

acts on the system, in

what interval of time would the flywheel come to rest?

a. 3.5 min

b. 7.0 min

c. 14 min**d. 21 min** **– correct**

An initially installed flywheel can store 106

J of kinetic energy when rotating at 300 rad/s. It

is replaced by another flywheel of the same size but made of a lighter and

stronger material.

If its mass is half that of the original and it is now capable of achieving a

rotational speed of

600 rad/s, what maximum energy can be stored?

a. 40 × 105 J**b. 20 × 105 J** **– correct**

c. 10 × 105 J

d. 5.0 × 105 J

A meter stick is hinged at its lower

end and allowed to fall from a vertical position. If its

moment of inertia is ML2

/3, with what angular speed does it hit the table?**a. 5.42 rad/s** **– correct**

b. 2.71 rad/s

c. 1.22 rad/s

d. 7.67 rad/s

A bus is designed to draw its power

from a rotating flywheel that is brought up to its

maximum speed (3 000 rpm) by an electric motor. The flywheel is a solid

cylinder of mass

500 kg and radius 0.500 m (Icylinder = MR2

/2). If the bus requires an average power of 10.0

kW, how long will the flywheel rotate?

a. 154 s**b. 308 s** **– correct**

c. 463 s

d. 617 s

An object of radius R and moment of inertia I rolls down an incline of

height H after starting

from rest. Its total kinetic energy at the bottom of the incline:

a. is gR/I.

b. is I/gH.

c. is 0.5 Ig/H.**d. cannot be found from the given information alone.** **– correct**

A uniform solid sphere rolls down an

incline of height 3 m after starting from rest. In order

to calculate its speed at the bottom of the incline, one needs to know:

a. the mass of the sphere.

b. the radius of the sphere.

c. the mass and the radius of the sphere.**d. no more than is given in the problem.** **– correct**

wire ring of circumference 12.0 cm. What is the surface tension of the fluid?**a. 0.055 N/m – correct**

b. 0.11 N/m

c. 0.035 N/m

d. 0.018 N/m

Consider the use of the terms “rotation” and “revolution”. In physics:

a. the words are used interchangeably.

b. the words are used interchangeably but “rotation” is the preferred word.**c. the words have different meaning.** **– correct**

d. “rotation” is the correct word and “revolution” should not be used.

A solid disk of radius R rolls down

an incline in time T. The center of the disk is removed up

to a radius of R/2. The remaining portion of the disk with its center gone is

again rolled

down the same incline. The time it takes is:

a. T.**b. more than T**. **– correct**

c. less than T.

d. requires more information than given in the problem to figure out.

The quantity “angular

momentum” (in terms of the fundamental quantities of mass, length,

and time) is equivalent to:

a. MLT−2

.**b. ML2 T−1** **– correct**

.

c. ML2

T−3

.

d. ML3

T.

A ventilation fan with a moment of inertia of 0.034 kg⋅m2

has a net torque of 0.11 N⋅m

applied to it. If it starts from rest, what angular momentum will it have 8.0 s

later?**a. 0.88 kg⋅m2/s** **– correct**

b. 0.97 kg⋅m2/s

c. 2.0 kg⋅m2/s

d. 3.25 kg⋅m2/s

A figure skater with arms initially

extended starts spinning on the ice at 3 rad/s. She then

pulls her arms in close to her body. Which of the following results?

a. a smaller rotational rate**b. a greater rotational rate** **– correct**

c. a greater angular momentum

d. a smaller angular momentum

An ice skater spins at 2.5 rev/s when

his arms are extended. He draws his arms in and spins at

6.0 rev/s. By what factor does his moment of inertia change in the process?

a. 2.4

b. 1.0**c. 0.42** **– correct**

d. 0.12

A figure skater on ice with arms extended, spins at a rate of 2.5 rev/s.

After he draws his arms

in, he spins at 6.0 rev/s. By what factor does the skater’s kinetic energy

change when he

draws his arms in?**a. 2.4** **– correct**

b. 1.0

c. 0.42

d. 0.12

70. A turntable has a moment of inertia of 3.00 × 10−2

kg⋅m2

and spins freely on a frictionless

bearing at 25.0 rev/min. A 0.300-kg ball of putty is dropped vertically onto

the turntable and

sticks at a point 0.100 m from the center. What is the new rate of rotation of

the system?

a. 40.8 rev/min**b. 22.7 rev/min** **– correct**

c. 33.3 rev/min

d. 27.2 rev/min

A turntable has a moment of inertia of 3.00 × 10−2

kg⋅m2

and spins freely on a frictionless

bearing at 25.0 rev/min. A 0.300-kg ball of putty is dropped vertically on the

turntable and

sticks at a point 0.100 m from the center. By what factor does the angular momentum

of the

system change after the putty is dropped onto the turntable?

a. 1.22**b. 1.00 (no change)** **– correct**

c. 0.820

d. 1.50

A turntable has a moment of inertia

of 3.0 × 10−2

kg⋅m2

and spins freely on a frictionless

bearing at 25 rev/min. A 0.30-kg ball of putty is dropped vertically on the

turntable and sticks

at a point 0.10 m from the center. By what factor does the kinetic energy of

the system

change after the putty is dropped onto the turntable?**a. 0.91** **– correct**

b. 1.0

c. 0.82

d. 1.5

A cylinder (I = MR2/2) is rolling along the ground at 7.0 m/s. It comes to a hill and starts

going up. Assuming no losses to friction, how high does it get before it stops?

a. 1.2 m**b. 3.7 m** **– correct**

c. 4.2 m

d. 5.9 m