

CHAPTER THREE
Forces
MULTIPLE CHOICE QUESTIONS
Multiple Choice 3.1
Correct Answer (e)
the acceleration on Earth and the planet are:
Multiple Choice 3.3
Correct Answer (a). The gravitational force is:
Multiple Choice 3.2
Correct Answer (d). The gravitational force between two objects of masses m1 and m2 at a distance d is:
Multiple Choice 3.4
Correct Answer (b). The gravitational force is:
Multiple Choice 3.5
Correct Answer (a) The
Multiple Choice 3.6
Correct Answer (d). From MC 3.5, the ratio of
is:
The masses of the two planets can be written as:
Multiple Choice 3.7
Correct Answer (c)
Multiple Choice 3.8
Correct Answer (d).
Multiple Choice 3.9
Correct Answer (d). The force between two charges q1 and q2 is:
The force is proportional to 1 r 2 . That means doubling the distance quarters the force. In this problem, we decrease the distance by 5 times, so the force increases by 52 times. So:
Multiple Choice 3.10
Correct Answer (c). The electric force is proportional to 1 r 2 , so if we increase the distance by a factor of three, the force is reduced by a factor of 32, or 9.
Multiple Choice 3.11
Correct Answer (d). The electric force is proportional to q , so if we double the magnitude of one the charges, the magnitude of the force between them increases to twice its former magnitude
Multiple Choice 3.12
Correct Answer (c).
Easy way: Doubling the distance reduces the force by a factor of 4. Since F is proportional to q, doubling one of the charges doubles the force
Combining these factors effects we get a factor of:
net force on q1 . The forces q2 and q3 each exerts on q1 are:
F12 = ( 9 × 109 Nm 2 C 2 ) (15 × 10 6 C) (13 × 10 6 C) ( 7.5 × 10 2 m ) 2
12 = 312 N

Figure 1
So, the force is reduced by a factor of 2.
Longer way: Let
Multiple Choice 3.13
Correct Answer (e). The electric force between two charges is:
F13 = ( 9 × 109 Nm 2 C 2 ) (15 × 10 6 C) (13 × 10 6 C) (12.5 × 10 2 m ) 2 F13 = 112 N
Figure 1 shows F12, F13, and its x- and y- components, which are:
F13, x = F13 cos 37° = 89 N
F13, y = F13 sin 37° = 67 N
So: F Net,x = F13, x ≈ 89 N
F Net,y = F12 + F13, y = 312 + 67 ≈ 380 N.
Multiple Choice 3.14
Correct Answer (a) The electric force between two charges is shown in Multiple Choice 3.13:
First, we calculate the forces q2 and q3 exert on q1. Then, find the x and y components of the forces, which are the components of the
26
F12 = k q1q2 r12 2
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LXV.—NORTH OF DENMARK PLACE.
To the north of Denmark Place the frontage to High Street seems to have been fully built on before 1658 (Plate 3). Originally the garden of the Hospital extended as far as here, for the limits of the parish of St. Margaret, Westminster, are described in 1222, as stretching along what is now Oxford Street as far as the Hospital garden.[672] In somewhat later times the principal feature of this triangular plot was The Crown inn and brewhouse, which is referred to as early as 1452[673] as “a brewhouse called The Crowne” with six cottages adjoining. It will be seen, therefore, that even at that date there were a number of buildings on this plot. Included in the portion of the Hospital’s property which fell to the share of Katherine Legh were “one close rent xijs and iiijd by the yere there goinge oute of a mese called The Crowne, and one chieff rente of vis by yere goyng oute of a brew house there, nowe so late in the tenure or occupacion of one Richard Lightfoot.” When next heard of The Crown brewhouse, with a close of 3 acres[674] and an orchard and garden adjoining, belonged to John Vavasour, whose son Nicholas in 1615 sold it to William Bowes.[675]
At a spot immediately opposite The Crown at one time stood the pound, and according to Maitland[676] , this was also the situation of the gallows, between the date of their removal from the Elms in Smithfield about the year 1413, and their further subsequent removal to Tyburn. It does not appear, however, that Maitland had any authority for the statement as to the removal of the gallows from Smithfield. As regards the further removal to Tyburn, if it ever took place it must have been before the year 1478, when it is quite certain that the gallows were already in the position occupied by them for centuries to come, viz., opposite the southern end of Edgware Road. There is, indeed, a very considerable probability that this was the
case even in Edward I.’s reign,[677] and it seems improbable that a permanent gallows ever stood in St. Giles at all.[678]
The pound was originally[679] in High Street, St. Giles, just to the west of where Endell Street now issues, and was removed thence in 1656 to the junction of High Street, Oxford Street and Tottenham Court Road.[680]
LXVI.—SITE OF “THE ROOKERY” (BAINBRIDGE STREET, LAWRENCE STREET, MAYNARD STREET, ARTHUR STREET BUCKNALL STREET).
Included in that part of the Hospital property which fell to Lord Lisle’s share was “one close lyinge before the greate gate there conteyninge by estimacion 16 acres, with appurtenances, nowe or late in the occupacion of Maister Magnus.”[681] From this description Parton had some justification in assuming that the ground covered the site of Baynbridge Street, Arthur Street, etc. If this is correct, however, the close must have been split up by the early part of Elizabeth’s reign, and that part which covered the sites of the streets in question was, in 1583, in the possession of George Harrison. On his death in that year it was found[682] that he was seized inter alia of “a close ... called Le Church Close in the parish of St. Giles, containing by estimation five acres of pasture.” He also owned 13 messuages with gardens on the north side of High Street, stretching westward from The Maidenhead, [683] which he had purchased from Lord Mountjoy,[684] but no record has been found which might enable the previous owners of Church Close to be traced. In 1632 John Barbor alias Grigge bought[685] a number of the houses, together with “all that close of meadow or pasture ... called ... Church Close alias Williamsfeild ... conteyning 5 acres,” and in 1649 the property was further transferred to Henry Bainbridge.[686]
Hollar’s Plan of 1658 (Plate 3) shows the commencement of building on this area, and Parton[687] notes that Bainbridge Street and Buckridge Street were built on before 1672. These two streets, with Maynard Place and Dyott Street, obviously took their names from the persons mentioned in a fine of 1676,[688] from which it
seems probable that Maynard, Buckridge and Dyott were the married names of Bainbridge’s three daughters. Church Lane and Church Street had obvious reference to Church Close. The locality subsequently became one of the most disreputable districts in London,[689] a state of things which was finally put an end to by driving New Oxford Street[690] through the midst. At the same time several of the old streets were abolished, and some of those which remained had their names altered.
P , W C D , E .:—
In the collection of water colour drawings by J. W. Archer, preserved at the British Museum are three of The Rookery, representing: Entrance from High Street.
Part of The Rookery in 1844.
A cellar in The Rookery.
In the Heal Collection, preserved in the Holborn Public Library, are a series of views illustrating The Rookery.
LXVII.—N . 100, 101 102, GREAT RUSSELL STREET.
G .
His Grace the Duke of Bedford, K.G.