Conceptual Physics Chapter 8 Answers
Trouble one
An object is executing circular motion. What is the direction of instantaneous linear speed?
Lisa T.
Numerade Educator
Trouble 2
On a rotating turntable, does tangential speed or rotational speed vary with distance from the center?
Kara Thousand.
Numerade Educator
Problem 3
A tapered cup rolled on a flat surface makes a circular path. What does this tell y'all nearly the tangential speed of the rim of the broad finish of the cup compared with that of the rim of the narrow end?
Lisa T.
Numerade Educator
Problem 4
How does the tapered rim of a wheel on a railroad train let i part of the rim to have a greater tangential speed than another function when it is rolling on a track?
Kara G.
Numerade Educator
Problem 5
What is rotational inertia, and how is it like to inertia as studied in before chapters?
Lisa T.
Numerade Educator
Problem six
Tin two objects accept the same inertia but a different moment of inertia?
Kara M.
Numerade Educator
Trouble 7
Every bit distance increases between most of the mass of an object and its center of rotation, does rotational inertia increase or decrease?
Lisa T.
Numerade Educator
Problem 8
Consider three axes of rotation for a pencil: along the pb, at correct angles to the lead at the heart, and at right angles to the lead at one end. Rate the rotational inertias nearly each axis from smallest to largest.
Kara M.
Numerade Educator
Problem 9
Which is easier to get swinging: a baseball bat held at the narrow stop or a bat held closer to the massive end (high-strung up)?
Lisa T.
Numerade Educator
Problem 10
Why does angle your legs when running enable y'all to swing your legs to and fro more rapidly?
Kara M.
Numerade Educator
Problem 11
An object is rolling down an incline, what is the relationship between its dispatch and its rotational inertia?
Lisa T.
Numerade Educator
Problem 12
How is torque similar to strength?
Kara G.
Numerade Educator
Trouble 13
When does a forcefulness produce nil torque?
Lisa T.
Numerade Educator
Trouble 14
How do clockwise and counterclockwise torques compare when a system is balanced?
Kara One thousand.
Numerade Educator
Trouble 15
If y'all toss a stick into the air, it appears to wobble all over the place. Specifically, well-nigh what place does information technology wobble?
Lisa T.
Numerade Educator
Problem 16
Where is the centre of mass of a baseball? Where is its center of gravity? Where are these centers for a baseball bat?
Kara M.
Numerade Educator
Problem 17
If you hang at residue by your easily from a vertical rope, where is your heart of gravity with respect to the rope?
Lisa T.
Numerade Educator
Trouble 18
Is the center of mass of an irregularly shaped trunk its geometric eye?
Kara 1000.
Numerade Educator
Problem 19
What is the relationship betwixt the center of gravity and the back up base for an object that is in stable equilibrium?
Lisa T.
Numerade Educator
Problem 20
Why doesn't the Leaning Tower of Pisa topple over?
Kara Chiliad.
Numerade Educator
Trouble 21
In terms of center of gravity, support base of operations, and torque, why can't you stand with your heels and back to a wall and and then bend over to touch your toes and render to your stand-up position?
Lisa T.
Numerade Educator
Problem 22
When you whirl a tin can tied at the end of a string in a circular path, why do you need to keep pulling on the cord? What is the role of the string?
Kara M.
Numerade Educator
Problem 23
Is information technology an inward force or an outward forcefulness that is exerted on the clothes during the spin wheel of an automatic washing machine?
Eric M.
Numerade Educator
Problem 24
If the string that holds a whirling can in its round path breaks, what kind of force causes it to motility in a direct line path: centripetal, centrifugal, or no strength? What law of physics supports your answer?
Kara G.
Numerade Educator
Problem 25
If you are not wearing a seat belt in a auto that rounds a curve, and you slide across your seat and slam against a car door, what kind of force is responsible for your slide: centripetal, centrifugal, or no forcefulness? Why is the right answer "no forcefulness"?
Sheh Lit C.
Academy of Washington
Problem 26
Why is centrifugal force in a rotating frame called a "fictitious forcefulness"?
Kara M.
Numerade Educator
Problem 27
How tin gravity be simulated in an orbiting infinite station?
Lisa T.
Numerade Educator
Problem 28
How is angular momentum related to inertia?
Kara M.
Numerade Educator
Problem 29
What is the law of inertia for rotating systems in terms of angular momentum?
Lisa T.
Numerade Educator
Problem 30
If a skater who is spinning pulls her arms in so as to reduce her rotational inertia by half, by how much volition her angular momentum change? Past how much will her charge per unit of spin increase? (Why do your answers differ?)
Kara G.
Numerade Educator
Problem 31
Contact Grandpa and tell him how y'all're learning to distinguish between closely related concepts, using the examples of forcefulness and torque. Tell him how the two are similar and how they differ. Suggest where he can find "hands-on" things in his home to illustrate the divergence between the ii. Also cite an example that shows how the net force on an object tin be nada while the net torque isn't, as well as an example of the other fashion effectually. (Now make your Grandpa's day and ship an actual letter to him!)
Khoobchandra A.
Numerade Educator
Problem 32
Fasten a pair of foam cups together at their wide ends and roll them along a pair of meter sticks that simulate railroad tracks. Notation how they self-correct whenever their path departs from the middle. Question: If yous taped the cups together at their narrow ends, and so they tapered oppositely as shown, would the pair of cups cocky-correct or self-destruct when rolling slightly off centre?
Kara Grand.
Numerade Educator
Problem 33
Spike a fork, spoon, and wooden match together as shown in the sketch. The combination will remainder nicely—on the edge of a glass, for example. This happens because the center of gravity actually "hangs" below the signal of support.
Salamat A.
Numerade Educator
Problem 34
Stand with your heels and back against a wall and endeavour to curve over and touch your toes. You'll find that you have to stand abroad from the wall to do so without toppling over. Compare the minimum distance of your heels from the wall with the distance for a friend of the opposite sex. Who can bear upon their toes with their heels nearer to the wall: men or women? On the average and in proportion to height, which sex has the lower center of gravity?
Kara Yard.
Numerade Educator
Problem 35
First ask a friend to stand facing a wall with her toes touching the wall. Then ask her to stand up on the balls of her feet without toppling backward. Your friend won't be able to do it. Now you explicate why it can't be washed.
Lisa T.
Numerade Educator
Problem 36
Residuum a meter stick on two extended forefingers every bit shown. Slowly bring your fingers together. At what part of the stick do your fingers meet? Can you lot explain why this always happens, no matter where you outset your fingers?
Kara M.
Numerade Educator
Problem 37
Place the hook of a wire coat hanger over your finger. Carefully rest a coin on the directly wire on the bottom directly nether the claw. You may accept to flat- 10 the wire with a hammer or fashion a tiny platform with tape. With a surprisingly small corporeality of exercise you can swing the hanger and
counterbalanced coin back and forth and and so in a circle. Centripetal force holds the coin in identify.
Salamat A.
Numerade Educator
Problem 38
Torque $=$ lever arm $\times$ force
Summate the torque produced past a 100-N perpendicular force at the end of a 0.3-g-long wrench.
Kara M.
Numerade Educator
Problem 39
Torque $=$ lever arm $\times$ force
How does the torque produced change if the force reduces to fifty N while keeping the length of the wrench unchanged?
Lisa T.
Numerade Educator
Problem 40
Centripetal force: $F=chiliad v^{2} / r$
A horizontal cord whirls a 1-kg can in a circle of radius 2 grand with a speed of 2 g/s. Calculate the tension in the cord.
Kara M.
Numerade Educator
Problem 41
Centripetal force: $F=m 5^{2} / r$
Calculate the forcefulness of friction that keeps an fourscore-kg person sitting on the edge of a horizontal rotating platform when the person sits two m from the heart of the platform and has a tangential speed of 3 m/s.
Lisa T.
Numerade Educator
Problem 42
Athwart momentum $=m v r$
Calculate the angular momentum of the whirling tin in trouble 40.
Kara M.
Numerade Educator
Problem 43
Angular momentum $=chiliad five r$
If a person's speed doubles and all else remains the same, what will be the person'south angular momentum?
Lisa T.
Numerade Educator
Problem 44
The bore of the base of a tapered drinking cup is 6 cm. The diameter of its mouth is 9 cm. The path of the cup curves when yous roll it on the top of a table. Which end, the base or the oral fissure, rolls faster? How much faster?
Kara Yard.
Numerade Educator
Problem 45
To tighten a commodities, you push with a forcefulness of 80 Due north at the end of a wrench handle that is 0.25 m from the centrality of the bolt.
a. What torque are y'all exerting?
b. You lot movement your hand in to be merely 0.10 chiliad from the commodities. To attain the same torque, show that yous should exert 200 N of force.
c. Do your answers depend on the management of your push button relative to the direction of the wrench handle?
Lisa T.
Numerade Educator
Problem 46
The rock and meter stick residuum at the 25-cm marker, as shown in the sketch. The meter stick has a mass of 1 kg. What must exist the mass of the rock?
Kara Grand.
Numerade Educator
Problem 47
In ane of the photos at the beginning of this chapter, Mary Beth uses a torque feeler that consists of a meter stick held at the 0-cm end with a weight dangling from various positions along the stick. When the stick is held horizontally, torque is produced when a 1-kg object hangs from the 50-cm mark. How much more torque is exerted when the object is hung from the 75-cm mark? The 100-cm mark?
Lisa T.
Numerade Educator
Trouble 48
An ice puck of mass m revolves on an icy surface in a circle at speed v at the end of a horizontal cord of length L. The tension in the string is T.
a. Write the equation for centripetal force, and substitute the values T and L appropriately. Then, with a flake of uncomplicated algebra, rearrange the equation so that information technology solves for mass.
b. Show that the mass of the puck is 5 kg when the length of the string is ii one thousand, the string tension is 10 Northward, and the tangential speed of the puck is ii m/s.
Kara Thousand.
Numerade Educator
Problem 49
If a trapeze artist rotates once each second while sailing through the air and contracts to reduce her rotational inertia to one-third of what information technology was, how many rotations per second will effect?
Sheh Lit C.
Academy of Washington
Trouble 50
A minor infinite telescope at the terminate of a tether line of length L moves at linear speed 5 about a cardinal space station.
a. What will be the linear speed of the telescope if the length of the line is reduced to 0.33 50?
b. If the initial linear speed of the telescope is one.0 m/due south, what is its speed when pulled in to one-third its initial altitude from the space station?
Kara M.
Numerade Educator
Problem 51
The 3 cups are rolled on a level surface. Rank the cups by how far they depart from a straight-line path (nigh curved to to the lowest degree curved).
Lisa T.
Numerade Educator
Trouble 52
Three types of rollers are placed on slightly inclined parallel meter stick tracks equally shown. From greatest to to the lowest degree, rank the rollers in terms of their power to remain stable as they gyre.
Kara M.
Numerade Educator
Problem 53
Get-go from a rest position, a solid disk A, a solid ball B, and a hoop C race down an inclined plane. Rank them in reaching the lesser: winner, second place, and third identify.
Linda West.
Numerade Educator
Problem 54
Yous concur a meter stick at 1 cease with the same mass suspended at the reverse end. Rank the torque needed to keep the stick steady, from largest to smallest.
Kara M.
Numerade Educator
Problem 55
Three physics majors in skilful physical shape stand with their backs against a wall. Their task is to lean over and touch on their toes without toppling over. Rank their chances for success from highest to lowest.
Samuel S.
Numerade Educator
Problem 56
While riding on a funfair Ferris wheel, Sam Nasty horses around and climbs out of his chair and along the spoke and so that he is halfway to the axis. How does his rotational speed compare with that of his friends who remain in the chair? How does his tangential speed compare? Why are your answers dissimilar?
Kara G.
Numerade Educator
Problem 57
Dan and Sue wheel at the aforementioned speed. The tires on Dan'south bike are larger in bore than those on Sue'south wheel. Which wheels, if either, take the greater rotational speed?
Lisa T.
Numerade Educator
Trouble 58
Apply the equation $v=r \omega$ to explain why the end of a flyswatter moves much faster than your wrist when you swat a wing.
Kara K.
Numerade Educator
Problem 59
The wheels of railroad trains are tapered, a feature especially important on curves. How, if at all, does the amount of taper relate to how great the sharpness of curves tin be?
Lisa T.
Numerade Educator
Problem threescore
Flamingos are oft seen standing on i leg with the other leg lifted. Is rotational inertia enhanced with long legs? What can you say most the bird'due south center of mass with respect to the human foot on which it stands?
Kara M.
Numerade Educator
Trouble 61
The front wheels of a racing vehicle are located far out in front end to assist go along the vehicle from nosing upwards when it accelerates. What physics concepts play a role here?
Lisa T.
Numerade Educator
Problem 62
Which will have the greater acceleration rolling down an incline: a bowling ball or a volleyball? Defend your reply.
Kara M.
Numerade Educator
Problem 63
A softball and a basketball beginning from rest and coil down an incline. Which brawl reaches the lesser beginning? Defend your answer.
Lisa T.
Numerade Educator
Problem 64
Is the net torque changed when a partner on a seesaw stands or hangs from her end instead of sitting? (Does the weight or the lever arm modify?)
Kara One thousand.
Numerade Educator
Trouble 65
Can a force produce a torque when there is no lever arm?
Lisa T.
Numerade Educator
Problem 66
When you pedal a bicycle, maximum torque is produced when the pedal sprocket arms are in the horizontal position, and no torque is produced when they are in the vertical position. Explain.
Kara M.
Numerade Educator
Problem 67
When the line of activeness of a force intersects the center of mass of an object, can that forcefulness produce a torque about the object'due south center of mass?
Lisa T.
Numerade Educator
Problem 68
When a bowling brawl leaves your mitt, it may not spin. But further along the alley, it does spin. What produces the spinning?
Kara M.
Numerade Educator
Trouble 69
Why does sitting closest to the heart of a vehicle provide the most comfortable ride in a bus traveling on a bumpy road, in a transport in a choppy sea, or in an airplane in turbulent air?
Lisa T.
Numerade Educator
Problem lxx
Bold your anxiety are not held downward, which is more than difficult: doing sit-ups with your knees bent or with your legs straight out?
Kara Chiliad.
Numerade Educator
Trouble 71
Explain why a long pole is more beneficial to a tightrope walker if the pole droops.
Christopher D.
Numerade Educator
Problem 72
Why must you lot bend forrad when carrying a heavy load on your back?
Kara M.
Numerade Educator
Trouble 73
Why is the wobbly motion of a unmarried star an indication that the star has one or more planets orbiting effectually it?
Lisa T.
Numerade Educator
Trouble 74
Why is it easier to deport the aforementioned amount of water in two buckets, i in each hand, than in a unmarried saucepan?
Kara 1000.
Numerade Educator
Problem 75
Where is the center of mass of World'southward temper?
Lisa T.
Numerade Educator
Trouble 76
Using the ideas of torque and heart of gravity, explicate why a ball rolls down a colina.
Kara Grand.
Numerade Educator
Problem 77
Why is it important to secure file cabinets to the flooring, especially cabinets with heavy loads in the pinnacle drawers?
Lisa T.
Numerade Educator
Problem 78
Depict the comparative stabilities of the 3 objects shown in terms of piece of work and potential energy.
Kara M.
Numerade Educator
Problem 79
The centers of gravity of the three trucks parked on a colina are shown by the X s. Which truck(s) will tip over?
Lisa T.
Numerade Educator
Problem 80
A racing car on a flat circular rails needs friction between the tires and the rails to maintain its round motion. How much more friction is required for twice the speed?
Kara K.
Numerade Educator
Problem 81
An object is moving with abiding speed in a circular path. Is a force interim on it?
Lisa T.
Numerade Educator
Problem 82
Equally a car speeds upwards when rounding a curve, does the centripetal forcefulness on the car also increase? Defend your reply.
Kara M.
Numerade Educator
Problem 83
When you are in the front passenger seat of a car turning to the left, you may find yourself pressed against the right-side door. Why do you press against the door? Why does the door press on you? Does your explanation involve a centrifugal force or Newton'southward laws?
Sheh Lit C.
University of Washington
Problem 84
Friction is needed for a car rounding a curve. Merely, if the road is banked, friction may not be required at all. What, so, supplies the needed centripetal force? (Hint: Consider vector components of the normal force on the car.)
Kara M.
Numerade Educator
Problem 85
Under what conditions could a fast-moving car remain on a banked track covered with slippery ice?
Lisa T.
Numerade Educator
Problem 86
Explain why a centripetal force does not do work on a circularly moving object.
Kara M.
Numerade Educator
Problem 87
The occupant within a rotating infinite habitat of the futurity feels that she is existence pulled by artificial gravity confronting the outer wall of the habitat (which becomes the "floor"). Explain what is going on in terms of Newton'south laws and centripetal force.
Christopher D.
Numerade Educator
Trouble 88
The sketch shows a coin at the border of a turntable. The weight of the coin is shown by the vector $West$.Ii other forces act on the coin - the normal force and a force of friction that prevents it from sliding off the edge. Draw force vectors for both of these.
Kara M.
Numerade Educator
Problem 89
A motorcyclist is able to ride on the vertical wall of a basin-shaped track as shown. Friction of the wall on the tires is shown past the vertical red vector. (a) How does the magnitude of this vertical vector compare with the weight of the motorcycle and passenger? (b) Does the horizontal red vector represent the normal force acting on the bike and rider, the centripetal strength, both, or neither? Defend your answer.
Sheh Lit C.
Academy of Washington
Trouble 90
The sketch shows a conical pendulum. The bob swings in a circular path. The tension $T$ and weight $Westward$ are shown by vectors. Describe a parallelogram with these vectors, and show that their resultant lies in the plane of the circle. (See the parallelogram rule in Chapter 2.) What is the name of this resultant force?
Kara M.
Numerade Educator
Problem 91
You sit at the center of a large turntable at an amusement park as it is set spinning and and then allowed to spin freely. When you clamber toward the border of the turntable, does the rate of the rotation increase, subtract, or remain unchanged? What physics principle supports your answer?
Christopher D.
Numerade Educator
Problem 92
Consider a brawl rolling around in a circular path on the inner surface of a cone. The weight of the ball is shown by the vector $Westward.$ Without friction, only one other force acts on the brawl—a normal forcefulness. (a) Depict in the vector for the normal strength. (The length of the vector depends on the next footstep, b.) (b) Using the parallelogram rule, show that the resultant of the ii vectors is along the radial direction of the ball's circular path. (Yeah, the normal is appreciably greater than the weight!)
Kara Thou.
Numerade Educator
Problem 93
A sizable quantity of soil is washed down the Mississippi River and deposited in the Gulf of United mexican states each year. What effect does this tend to have on the length of a day? (Hint: Chronicle this to Figure 8.52.)
Lisa T.
Numerade Educator
Problem 94
If all of World's inhabitants moved to the equator, how would this touch World'due south rotational inertia? How would it affect the length of a day?
Kara M.
Numerade Educator
Problem 95
Strictly speaking, as more and more skyscrapers are congenital on the surface of Earth, does the day tend to become longer or shorter? And, strictly speaking, does the falling of autumn leaves tend to lengthen or shorten the 24-hour twenty-four hours? What physics principle supports your answers?
Sheh Lit C.
University of Washington
Problem 96
If the world'due south populations moved to the North Pole and the South Pole, would the 24-hour day get longer, shorter, or stay the same?
Kara M.
Numerade Educator
Problem 97
If the polar water ice caps on Earth's solid surface were to cook, the oceans would be deeper. Strictly speaking, what effect would this take on Earth's rotation?
Lisa T.
Numerade Educator
Problem 98
Why does a typical modest helicopter with a single main rotor take a second small rotor on its tail? Describe the consequence if the pocket-size rotor fails in flight.
Kara One thousand.
Numerade Educator
Problem 99
We believe that our milky way was formed from a huge cloud of gas. The original deject was far larger than the present size of the galaxy, was more or less spherical, and was rotating much more slowly than the galaxy is now. In this sketch, we come across the original cloud and the galaxy as it is now (seen edgewise). Explain how the inward pull of gravity and the conservation of athwart momentum contribute to the galaxy's nowadays shape and why it rotates faster now than when it was a larger, spherical cloud.
Christopher D.
Numerade Educator
Problem 100
Earth is non spherical just bulges at the equator. Jupiter bulges more. What is the cause of these bulges?
Kara Grand.
Numerade Educator
Problem 101
An automobile speedometer is configured to read speed proportional to the rotational speed of its wheels. If the oversize wheels of this red car were installed with- out making speedometer corrections, talk over whether the speedometer reading will exist high, or low—or no change.
Salamat A.
Numerade Educator
Trouble 102
A large wheel is coupled to a wheel with half the diameter, equally shown in the sketch. How does the rotational speed of the smaller wheel compare with that of the larger wheel? Discuss the comparisons of the tangential speeds at the rims (assuming the belt doesn't slip).
Kara M.
Numerade Educator
Problem 103
In this chapter, we learned that an object may not be in mechanical equilibrium even when $\Sigma F=0.$ Talk over what else defines mechanical equilibrium.
Salamat A.
Numerade Educator
Trouble 104
When a auto drives off a cliff information technology rotates forrad every bit it falls. For a higher speed off the cliff, talk over whether the car will rotate more or less. (Consider the time that the unbalanced torque acts.)
Kara M.
Numerade Educator
Problem 105
Discuss why a car noses up when accelerating and noses down when braking.
Salamat A.
Numerade Educator
Problem 106
Hash out how a ramp would help you to distinguish between two identical-looking spheres of the same weight, one solid and the other hollow.
Kara Thousand.
Numerade Educator
Problem 107
Which volition curlicue down an incline faster: a can of water or a can of ice? Talk over and explain.
Salamat A.
Numerade Educator
Trouble 108
Why are lightweight tires preferred in wheel racing? Hash out and explicate.
Kara Grand.
Numerade Educator
Problem 109
A youngster who has entered a soapbox derby (in which four-wheel, unpowered vehicles roll from rest down a hill) asks if large massive wheels or lightweight ones should be used. Likewise, should the wheels have spokes or be solid? What communication do y'all offer?
Salamat A.
Numerade Educator
Problem 110
The spool is pulled in iii means, equally shown. In that location is sufficient friction for rotation. In what direction volition the spool ringlet in each case? Discuss and explain.
Kara M.
Numerade Educator
Problem 111
Nobody at the playground wants to play with the obnoxious boy, so he fashions a seesaw as shown so he can play without anyone else. Discuss how this is washed.
Christopher D.
Numerade Educator
Problem 112
How can the three bricks be stacked so that the pinnacle brick has maximum horizontal deportation from the bottom brick? For example, stacking them as suggested past the dashed lines would be unstable and the bricks would topple. (Hint: Start with the height brick and piece of work downwardly. At every interface the CG of the bricks above must not extend across the cease of the supporting brick.)
Kara M.
Numerade Educator
Problem 113
A long rails counterbalanced like a seesaw supports a golf ball and a more massive billiard ball with a compressed spring between the two. When the spring is released, the balls move away from each other. Does the track tip clockwise, tip counterclockwise, or remain in balance as the balls coil outward? What principles do you use for your discussion and explanation?
Salamat A.
Numerade Educator
Trouble 114
With respect to Diana'south finger, where is the center of mass of the plastic bird? Hash out how this residuum can be accomplished during its manufacture.
Kara M.
Numerade Educator
Problem 115
When a long-range cannonball is fired toward the equator from a northern (or southern) latitude, information technology lands west of its "intended" longitude. Discuss why this is so. (Hint: Consider a flea jumping from partway out to the outer border of a rotating turntable.)
Michael S.
Numerade Educator
Problem 116
Most oft we say that force causes acceleration. Only when Evan took a ride in a rocket sled at Bonneville Salt Flats, blood was forced to the back of his brain, nearly blacking him out. Talk over and identify the cause of this force.
Kara 1000.
Numerade Educator
Conceptual Physics Chapter 8 Answers,
Source: https://www.numerade.com/books/chapter/rotational-motion-5/
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