Deck 11: Rotational Dynamics and Static Equilibrium

Question 1

If an object remains at rest,then the sum of both the external torques and the external forces on the object must be zero.

Answer 1

True

Question 2

If the sum of the external forces on an object is zero,then the sum of the external torques on it must also be zero.

Answer 2

False

Question 3

Two equal-magnitude forces are applied to a door at the doorknob.The first force is applied perpendicular to the door,and the second force is applied at 30° to the plane of the door.Which force exerts the greater torque about the door hinge?

A)the first force (applied perpendicular to the door)
B)the second force (applied at an angle)
C)Both forces exert equal non-zero torques.
D)Both forces exert zero torque.

Answer 3

the first force (applied perpendicular to the door)

Question 4

A 95-N force exerted at the end of a 0.32-m long torque wrench produces a torque of 15 N ∙ m.What is the angle (less than 90°)between the wrench handle and the direction of the applied force?

A)30°
B)24°
C)36°
D)42°

Question 5

When a car is weighed,it is driven slowly on a horizontal floor over a scale that records a reading as the front wheels go over the scale,and then records a second reading as the rear wheels go over the scale.The weight of the car is equal to

A)the weight under the front wheels.
B)the weight under the rear wheels.
C)the average of the two weights.
D)the sum of the two weights.
E)the difference of the two weights.

Question 6

A force of 17 N is applied to the end of a 0.63-m long torque wrench at an angle 45° from a line joining the pivot point to the handle.What is the magnitude of the torque about the pivot point produced by this force?

A)7.6 N ∙ m
B)10.7 N ∙ m
C)12.0 N ∙ m
D)9.7 N ∙ m

Question 7

A spinning ice skater on extremely smooth ice is able to control the rate at which she rotates by pulling in her arms.Which of the following statements are true about the skater during this process? (There could be more than one correct choice. )

A)Her angular momentum remains constant.
B)Her moment of inertia remains constant.
C)Her kinetic energy remains constant.
D)She is subject to a constant non-zero torque.

Question 8

If the sum of the external torques on an object is zero,then the sum of the external forces on it must also be zero.

Question 9

A merry-go-round spins freely when Diego moves quickly to the center along a radius of the merry-go-round.As he does this,it is true to say that

A)the moment of inertia of the system decreases and the angular speed increases.
B)the moment of inertia of the system decreases and the angular speed decreases.
C)the moment of inertia of the system decreases and the angular speed remains the same.
D)the moment of inertia of the system increases and the angular speed increases.
E)the moment of inertia of the system increases and the angular speed decreases.

Question 10

As shown in the figure,a given force is applied to a rod in several different ways.In which case is the torque about the pivot P due to this force the greatest?

A)1
B)2
C)3
D)4
E)5

Question 11

A croquet mallet balances when suspended from its center of mass,as shown in the left part of the figure.If you cut the mallet into two pieces at its center of mass,as shown in the right part of the figure,how do the masses of the two pieces compare? (There could be more than one correct choice. )

A)The masses are equal.
B)The piece with the head of the mallet has the greater mass.
C)The piece with the head of the mallet has the smaller mass.
D)It is impossible to tell.

Question 12

A man in a gym is holding an 8.0-kg weight at arm's length,a distance of 0.55 m from his shoulder joint.What is the torque about his shoulder joint due to the weight if his arm is held at 30° below the horizontal?

A)22 N ∙ m
B)2.2 N ∙ m
C)4.4 N ∙ m
D)13 N ∙ m
E)37 N ∙ m

Question 13

A person sits on a freely spinning lab stool that has no friction in its axle.When this person extends her arms,

A)her moment of inertia decreases and her angular speed increases.
B)her moment of inertia decreases and her angular speed decreases.
C)her moment of inertia increases and her angular speed increases.
D)her moment of inertia increases and her angular speed decreases.
E)her moment of inertia increases and her angular speed remains the same.

Question 14

If the sum of both the external torques and the external forces on an object is zero,then the object must be at rest.

Question 15

A man in a gym is holding an 8.0-kg weight at arm's length,a distance of 0.55 m from his shoulder joint.What is the torque about his shoulder joint due to the weight if his arm is horizontal?

A)0.24 N ∙ m
B)4.4 N ∙ m
C)43 N ∙ m
D)15 N ∙ m
E)0 N ∙ m

Question 16

The lug nuts on a car wheel require tightening to a torque of 90 N ∙ m.If a 30-cm long wrench is used,what is the magnitude of the minimum force required using the wrench?

A)300 N
B)150 N
C)30 N
D)15 N

Question 17

Five forces act on a rod that is free to pivot at point P,as shown in the figure.Which of these forces is producing a counter-clockwise torque about point P? (There could be more than one correct choice. )

A)force A
B)force B
C)force C
D)force D
E)force E

Question 18

When is the angular momentum of a system constant?

A)Only when its total kinetic energy is constant.
B)Only when no net external force acts on the system.
C)Only when the linear momentum and the energy are constant.
D)Only when no net external torque acts on the system.
E)Only when the moment of inertia is constant.

Question 19

Two forces produce equal torques on a door about the door hinge.The first force is applied at the midpoint of the door;the second force is applied at the doorknob.Both forces are applied perpendicular to the door.Which force has a greater magnitude?

A)the first force (at the midpoint)
B)the second force (at the doorknob)
C)The two forces are equal.

Question 20

If the answer to your calculation has units of kg ∙ m²/s,what type of quantity could it be? (There could be more than one correct choice).

A)force
B)work
C)angular momentum
D)linear momentum
E)power

Question 21

A cinder block of mass m = 4.0 kg is hung from a nylon string that is wrapped around a frictionless pulley having the shape of a cylindrical shell,as shown in the figure.If the cinder block accelerates downward at 4.90 m/s² when it is released,what is the mass M of the pulley?

A)2.0 kg
B)4.0 kg
C)6.0 kg
D)8.0 kg
E)10 kg

Question 22

A uniform 1200-N piece of medical apparatus that is 3.5 m long is suspended horizontally by two vertical wires at its ends.A small but dense 550-N weight is placed on the apparatus 2.0 m from one end,as shown in the figure.What are the tensions,A and B,in the two wires?

A)A = 880 N,B = 880 N
B)A = 840 N,B = 910 N
C)A = 9000 N,B = 8200 N
D)A = 910 N,B = 840 N
E)A = 8200 N,B = 9000 N

Question 23

A torque of 12 N ∙ m is applied to a solid,uniform disk of radius 0.50 m.If the disk accelerates at
What is the mass of the disk?

A)60 kg
B)45 kg
C)30 kg
D)15 kg

Question 24

A force of
Is applied tangentially to a wheel of radius 0.340 m and causes an angular acceleration of 1.20 rad/s².What is the moment of inertia of the wheel?

A)4.78 kg ∙ m²
B)3.59 kg ∙ m²
C)5.98 kg ∙ m²
D)7.17 kg ∙ m²

Question 25

An irregularly shaped object that is 10 m long is placed with each end on a scale.If the scale on the right reads
While the scale on the left reads
How far from the left end is the center of gravity of this object?

A)5.7 m
B)7.4 m
C)4.3 m
D)14 m

Question 26

A 15-kg child is sitting on a playground teeter-totter,1.5 m from the pivot.What is the minimum distance,on the other side of the pivot,such that a 220-N force will make the child lift off the ground?

A)1.0 m
B)1.5 m
C)0.10 m
D)9.8 m
E)2.4 m

Question 27

The figure shows a person's foot.In that figure,the Achilles tendon exerts a force of magnitude F = 720 N.What is the magnitude of the torque that this force produces about the ankle joint?

A)12 N ∙ m
B)16 N ∙ m
C)21 N ∙ m
D)26 N ∙ m
E)36 N ∙ m

Question 28

A uniform solid cylinder of mass 10 kg can rotate about a frictionless axle through its center O,as shown in the cross-sectional view in the figure.A rope wrapped around the outer radius R₁ = 1.0 m exerts a force of magnitude F₁ = 5.0 N to the right.A second rope wrapped around another section of radius R₂ = 0.50 m exerts a force of magnitude F₂ = 6.0 N downward.How many radians does the cylinder rotate through in the first 5.0 seconds,if it starts from rest?

A)13 rad
B)7.5 rad
C)5.0 rad
D)10 rad

Question 29

In a laboratory experiment,a student brings up the rotational speed of a flywheel to 30.0 rpm.She then allows it to slow down on its own,and counts 240 revolutions before the apparatus uniformly comes to a stop.The moment of inertia of the flywheel is 0.0850 kg ∙ m².What is the magnitude of the retarding torque on the flywheel?

A)0.0425 N ∙ m
B)0.159 N ∙ m
C)0.0787 N ∙ m
D)0.000278 N ∙ m
E)0.0000136 N ∙ m

Question 30

A mechanic is examining the wheel of a bicycle to adjust the brake.With the bicycle off the ground,he manually rotates the wheel until it reaches an angular speed of 12.0 rad/s and then allows it to coast to a stop.If the wheel has a moment of inertia of 0.100 kg ∙ m²,and the wheel slows uniformly to a stop in 160 s,what is the magnitude of the retarding torque?

A)1.00 N ∙ m
B)0.00750 N ∙ m
C)0.0787 N ∙ m
D)1.33 N ∙ m
E)1.67 N ∙ m

Question 31

The drive chain in a bicycle is applying a torque of 0.850 N ∙ m to the wheel of the bicycle.You can treat the wheel as a thin uniform hoop (or ring)with a mass of 0.750 kg and a radius of 33.0 cm.What is the angular acceleration of the wheel?

A)10.4 rad/s²
B)20.8 rad/s²
C)5.20 rad/s²
D)3.43 rad/s²
E)1.06 rad/s²

Question 32

The drum shown in the figure has a radius of 0.40 m and a moment of inertia of 2.3
About an axis perpendicular to it through its center.The frictional torque at the drum axle is 3.0 N ∙ m.A 14-m length of rope is wound around the rim.The drum is initially at rest.A constant force is applied to the free end of the rope until the rope is completely unwound and slips off.At that instant,the angular speed of the drum is
The drum then slows down at a constant rate and comes to a halt.In this situation,what was the magnitude of the constant force applied to the rope?

A)51 N
B)40 N
C)29 N
D)18 N
E)7.5 N

Question 33

The rotating systems shown in the figure differ only in that the two identical movable masses are positioned a distance r from the axis of rotation (left),or a distance r/2 from the axis of rotation (right).If you release the hanging blocks simultaneously from rest,and call t_L the time taken by the block on the left and t_R the time taken by the block on the right to reach the bottom,respectively,then

A)t_L > t_R.
B)t_L = t_R.
C)t_L < t_R.

Question 34

A particular motor can provide a maximum torque of 110 N ∙ m.Assuming that all of this torque is used to accelerate a solid,uniform,cylindrical flywheel of mass 10.0 kg and radius 3.00 m,how long will it take for the flywheel to accelerate from rest to

A)3.33 s
B)2.83 s
C)4.03 s
D)4.36 s

Question 35

A meter stick balances at the 50.0-cm mark.If a mass of 50.0 g is placed at the 90.0-cm mark,the stick balances at the 61.3-cm mark.What is the mass of the meter stick?

A)127 g
B)178 g
C)89.7 g
D)32.6 g
E)73.4 g

Question 36

A uniform rod is 2.0 m long.It is hinged to a wall at its left end,and held in a horizontal position at its right end by a vertical very light string,as shown in the figure.What is the angular acceleration of the rod at the moment after the string is released if there is no friction in the hinge?

A)15 rad/s²
B)3.3 rad/s²
C)7.4 rad/s²
D)11 rad/s²
E)It cannot be calculated without knowing the mass of the rod.

Question 37

A uniform solid cylinder of mass 10 kg can rotate about a frictionless axle through its center O,as shown in the cross-sectional view in the figure.A rope wrapped around the outer radius R₁ = 1.0 m exerts a force of magnitude F₁ = 5.0 N to the right.A second rope wrapped around another section of radius R₂ = 0.50 m exerts a force of magnitude F₂ = 6.0 N downward.What is the angular acceleration of the cylinder?

A)1.0 rad/s²
B)0.60 rad/s²
C)0.40 rad/s²
D)0.80 rad/s²

Question 38

A 15-kg child is sitting on a playground teeter-totter,1.5 m from the pivot.What is the magnitude of the minimum force,applied 0.30 m on the other side of the pivot,that is needed to make the child lift off the ground?

A)75 N
B)740 N
C)23 N
D)44 N
E)66 N

Question 39

A 385-g tile hangs from one end of a string that goes over a pulley with a moment of inertia of 0.0125 kg.m². And a radius of 15.0 cm.A mass of 710 g hangs from the other end of the string.When the tiles are released,the larger one accelerates downward while the lighter one accelerates upward.The pulley has no friction in its axle and turns without the string slipping.What is the tension in the string on the side of the 710-g tile?

A)9.77 N
B)6.87 N
C)5.59 N
D)4.41 N
E)3.68 N

Question 40

As shown in the figure,a 35.30-kg box is attached to a light string that is wrapped around a cylindrical frictionless spool of radius 10.0 cm and moment of inertia 4.00 kg ∙ m².The spool is suspended from the ceiling,and the box is then released from rest a distance 3.50 m above the floor.How long does it take for the box to reach the floor?

A)2.97 s
B)2.85 s
C)0.892 s
D)4.18 s
E)5.89 s

Question 41

An athlete holds a 7.5-kg shot put in his hand with his lower arm horizontal,as shown in the figure.His lower arm has a mass of 2.8 kg and its center of gravity (or center of mass)is 12 cm from the elbow-joint pivot.How much force must the extensor muscle (which is
_M in the figure)in the upper arm exert on the lower arm?

A)100 N
B)500 N
C)1000 N
D)1500 N

Question 42

To determine the location of the center of mass (or center of gravity)of a car,the car is driven over a scale on a horizontal floor.When the front wheels are over the scale,the weight recorded by the scale is 5800 N,and when the rear wheels are over the scale,the scale reads 6500 N.The distance between the front and rear wheels is measured to be 3.20 m.How far behind the front wheels is the center of mass located?

A)0.845 m
B)1.50 m
C)1.59 m
D)1.69 m
E)1.72 m

Question 43

A child is trying to stack two uniform bricks,each 24 cm long,so they will protrude as far as possible over the edge of a table without tipping over,as shown in the figure.What is the maximum possible overhang distance d?

A)10 cm
B)12 cm
C)14 cm
D)16 cm
E)18 cm

Question 44

A 320-g ball and a 400-g ball are attached to the two ends of a string that goes over a pulley with a radius of 8.7 cm.Because of friction in its axle,the pulley does not begin to rotate.What is the magnitude of the frictional torque at the axle of the pulley if the system remains at rest when the balls are released?

A)0.068 N ∙ m
B)0.61 N ∙ m
C)0.079 N ∙ m
D)0.063 N ∙ m
E)0.00070 N ∙ m

Question 45

A store's sign has a mass of 20 kg and is 3.0 m long.It is uniform,so its center of gravity is at the center of the sign.It is supported horizontally by a small loose bolt attached to the wall at one end and by a wire at the other end,as shown in the figure.What is the tension in the wire?

A)460 N
B)230 N
C)120 N
D)200 N
E)300 N

Question 46

A 120-kg refrigerator that is 2.0 m tall and 85 cm wide has its center of mass at its geometrical center.You are attempting to slide it along the floor by pushing horizontally on the side of the refrigerator.The coefficient of static friction between the floor and the refrigerator is 0.30.Depending on where you push,the refrigerator may start to tip over before it starts to slide along the floor.What is the highest distance above the floor that you can push the refrigerator so that it will not tip before it begins to slide?

A)0.71 m
B)1.0 m
C)1.2 m
D)1.4 m
E)1.6 m

Question 47

A uniform,solid,cylindrical flywheel of radius 1.4 m and mass 15 kg rotates at
What is the magnitude of the flywheel's angular momentum?

A)40 kg ∙ m²/s
B)20 kg ∙ m²/s
C)80 kg ∙ m²/s
D)60 kg ∙ m²/s

Question 48

A 100-kg nonuniform boom that is 6.0 m long is loosely pinned at the pivot at P.A 600-kg concrete block is suspended from the end of the boom at A,as shown in the figure.The boom forms a 30° angle above the horizontal,and is supported by a 4.0-m cable between points D and B.Point B is 4.0 m from P,and point D is 4.0 m above P.The center of mass of the boom is at point C,which is 2.0 m from P.Assume that all the quantities shown in the figure are accurate to two significant figures.What is the tension in the cable connected between points B and D?

A)9,300 N
B)8,400 N
C)8,100 N
D)7,500 N
E)6,900 N

Question 49

A uniform 40-N board supports two children weighing 500 N and 350 N.If the support is at the center of the board and the 500-N child is 1.5 m from its center,how far is the 350-N child from the center?

A)1.1 m
B)1.5 m
C)2.1 m
D)2.7 m

Question 50

In the figure,a uniform ladder of weight 200 N and length 10 m leans against a perfectly smooth wall.A firefighter of weight 600 N climbs a distance x up the ladder.The coefficient of static friction between the ladder and the floor is 0.50.What is the maximum value of x for which the ladder will not slip?

A)3.9 m
B)5.0 m
C)6.0 m
D)6.3 m
E)8.4 m

Question 51

A mobile is shown in the figure.The horizontal supports have negligible mass.Assume that all the numbers given in the figure are accurate to two significant figures.What mass M is required to balance the mobile?

A)18 g
B)30 g
C)36 g
D)60 g
E)90 g

Question 52

Three solid,uniform,cylindrical flywheels,each of mass 65.0 kg and radius 1.47 m,rotate independently around a common axis through their centers.Two of the flywheels rotate in one direction at 8.94 rad/s,but the other one rotates in the opposite direction at 3.42 rad/s.Calculate the magnitude of the net angular momentum of the system.

A)1020 kg ∙ m²/s
B)1500 kg ∙ m²/s
C)975 kg ∙ m²/s
D)940 kg ∙ m²/s

Question 53

A 3.00-m-long ladder,weighing 200 N,leans against a smooth vertical wall with its base on a horizontal rough floor,a distance of 1.00 m away from the wall.The ladder is not completely uniform,so its center of gravity is 1.20 m from its base.What force of friction must the floor exert on the base of the ladder to prevent the ladder from sliding down?

A)93.3 N
B)130 N
C)28.3 N
D)102 N
E)150 N

Question 54

A stepladder consists of two halves that are hinged at the top and connected by a tie rod which keeps the two halves from spreading apart.In this particular instance,the two halves are 2.5 m long,the tie rod is connected to the center of each half and is 70 cm long.An 800-N person stands 3/5 of the way up the stepladder,as shown in the figure.The ladder is light enough that we can neglect its weight,and it rests on an extremely smooth floor.What is the tension in the tie rod? (Note: To solve this problem,it is helpful to imagine cutting the ladder in half vertically and consider the forces and torques acting on each half of the ladder. )

A)140 N
B)240 N
C)280 N
D)360 N
E)560 N

Question 55

A uniform rod weighs 40 N and is 1.0 m long.It is hinged to a wall at the left end,and held in a horizontal position at the right end by a vertical string of negligible weight,as shown in the figure.What is the magnitude of the torque due to the string about a horizontal axis that passes through the hinge and is perpendicular to the rod? The hinge is very small with negligible friction.

A)40 N ∙ m
B)10 N ∙ m
C)5.0 N ∙ m
D)20 N ∙ m
E)30 N ∙ m

Question 56

In a certain cyclotron,a proton of mass 1.67 × 10^-27 kg moves in a circle of diameter 1.6 m with an angular speed of 2.0 × 10⁶ rad/s.What is the angular momentum of the proton?

A)1.3 × 10^-21 kg ∙ m²/s
B)1.8 × 10^-21 kg ∙ m²/s
C)2.1 × 10^-21 kg ∙ m²/s
D)3.2 × 10^-21 kg ∙ m²/s

Question 57

A 40-kg uniform ladder that is 5.0 m long is placed against a smooth wall at a height of h = 4.0 m,as shown in the figure.The base of the ladder rests on a rough horizontal surface whose coefficient of static friction with the ladder is 0.40.An 80-kg bucket is suspended from the top rung of the ladder,just at the wall.What is the magnitude of the force that the ladder exerts on the wall?

A)740 N
B)1,300 N
C)980 N
D)900 N
E)1,100 N

Question 58

A 5.00-m-long uniform ladder,weighing 200 N,rests against a smooth vertical wall with its base on a horizontal rough floor,a distance of 1.20 m away from the wall.The coefficient of static friction between the ladder and the floor is 0.200.How far up the ladder,measured along the ladder,can a 600-N person climb before the ladder begins to slip?

A)1.50 m
B)1.26 m
C)1.05 m
D)3.95 m
E)4.56 m

Question 59

A uniform 135-g meter stick rotates about an axis perpendicular to the stick passing through its center with an angular speed of 3.50 rad/s.What is the magnitude of the angular momentum of the stick?

A)0.0394 kg ∙ m²/s
B)0.473 kg ∙ m²/s
C)0.0739 kg ∙ m²/s
D)0.158 kg ∙ m²/s
E)0.0236 kg ∙ m²/s

Question 60

A store's sign has a mass of 20 kg and is 3.0 m long.It is uniform,so its center of gravity is at the center of the sign.It is supported horizontally by a small loose bolt attached to the wall at one end and by a wire at the other end,as shown in the figure.What is the magnitude of the net force that the bolt exerts on the sign?

A)460 N
B)230 N
C)200 N
D)120 N
E)300 N

Question 61

Initially,a small 2.0-kg rock is whirling at the end of a very thin string in a circular path of radius 0.75 m on a horizontal frictionless surface,as shown in the figure.The initial tangential speed of the rock was 5.0 m/s.The string has been slowly winding around a vertical rod,and a few seconds later the length of the string has shortened to 0.25 m.What is the instantaneous speed of the mass at the moment the string reaches a length of 0.25 m?

A)3.9 m/s
B)9.3 m/s
C)15 m/s
D)225 m/s
E)75 m/s

Question 62

An ice skater has a moment of inertia of 5.0 kg ∙ m² when her arms are outstretched,and at this time she is spinning at 3.0 rev/s.If she pulls in her arms and decreases her moment of inertia to 2.0 kg ∙ m²,how fast will she be spinning?

A)2.0 rev/s
B)3.3 rev/s
C)7.5 rev/s
D)10 rev/s

Question 63

A puck moves on a horizontal air table.It is attached to a string that passes through a hole in the center of the table.As the puck rotates about the hole,the string is pulled downward very slowly and shortens the radius of rotation,so the puck gradually spirals in towards the center.By what factor will the puck's angular speed have changed when the string's length has decreased to one-half of its original length?

A)2
B)4
C)
D)1
E)1/2

Question 64

A 5.0-m radius playground merry-go-round with a moment of inertia of 2000 kg ∙ m² is rotating freely with an angular speed of 1.0 rad/s.Two people,each of mass 60 kg,are standing right outside the edge of the merry-go-round and suddenly step onto the edge with negligible speed relative to the ground.What is the angular speed of the merry-go-round right after the two people have stepped on?

A)0.20 rad/s
B)0.40 rad/s
C)0.60 rad/s
D)0.80 rad/s
E)0.67 rad/s

Question 65

A solid wooden door,90 cm wide by 2.0 m tall,has a mass of 35 kg.It is open and at rest.A small 500-g ball is thrown perpendicular to the door with a speed of 20 m/s and hits the door 60 cm from the hinged side,causing it to begin turning.The ball rebounds along the same line with a speed of 16.0 m/s relative to the ground.How much energy is lost during this collision?

A)30 J
B)16 J
C)15 J
D)13 J
E)4.8 J

Question 66

A light-weight potter's wheel,having a moment of inertia of
Is spinning freely at 40.0 rpm.The potter drops a small but dense lump of clay onto the wheel,where it sticks a distance 1.2 m from the rotational axis.If the subsequent angular speed of the wheel and clay is 32 rpm,what is the mass of the clay?

A)4.2 kg
B)2.8 kg
C)3.7 kg
D)4.6 kg

Question 67

A figure skater rotating at 5.00 rad/s with arms extended has a moment of inertia of 2.25 kg ∙ m².If he pulls in his arms so his moment of inertia decreases to 1.80 kg ∙ m²,what will be his new angular speed?

A)2.25 rad/s
B)4.60 rad/s
C)6.25 rad/s
D)0.81 rad/s

Question 68

A 40.0-kg child running at 3.00 m/s suddenly jumps onto a stationary playground merry-go-round at a distance 1.50 m from the axis of rotation of the merry-go-round.The child is traveling tangential to the edge of the merry-go-round just before jumping on.The moment of inertia about its axis of rotation is 600 kg ∙ m² and very little friction at its rotation axis.What is the angular speed of the merry-go-round just after the child has jumped onto it?

A)0.788 rad/s
B)0.261 rad/s
C)6.28 rev/s
D)2.00 rad/s
E)3.14 rev/s

Question 69

A solid wood door,90.0 cm wide by 2.00 m tall has a mass of 35.0 kg.It is open and at rest.A small 500-g ball is thrown perpendicular to the door with a speed of 20.0 m/s and hits the door 60.0 cm from the hinged side.The ball rebounds with a speed of 16.0 m/s along the same line.What is the angular speed of the door just after the collision with the ball?

A)0.127 rad/s
B)0.925 rad/s
C)1.14 rad/s
D)2.28 rad/s
E)4.57 rad/s