27 DEC 2
育教備韻: 頁三第張六第日六初月一十年由洋师马:MAH KIU YAT PO
韌日僑華
三期星
日五廿月二十年八六九一联公年七十五國民華中
育僑
1969
物理科
陸永熾·
13. Solu
PHYSICS (8)
(a)-Principle of Moments-
khen a body is in equilibrium, the sun of tris anticlockwise moments about any point is equal to the sum of the clockwise momenta. sbone) the same point.
Law of Flotatior
STĂ Floating body displaces its own weight
or the fluid in which it floses.
It./sec
(1) Bistance moved in the first minute)
Then, taking moments about the point of belan
SOVS - 48M (1)
By Archimedes Principle, when the metai 15
Immersed in water, its loss in weight is V guys,
and its weight in water (Vs - V) gm, wt.
Taking moments again about the point
50 178 - V) - (48 - 6}X
(2). Divide the Becond equation by the first:
'balancet
8x60
240 ft.
(111) Distance moved after 2 min.
15
x 12 x 6012
* 240,
The specific gravity of the metal 25
960 ft.
istance moved during the second manute
720 ft.
(b) To determine the specific gravity of a liquid
固
同
qura
www.Solution
ja) Speed and Velocity
Speed is the rata of change of distance time while velocity is the rate of change of distance moved with time in a specified direction. The former is a scalar quantity, it has no direction by magnitude only. The latter has pʊʊa direction and menitude.
Velocity and acceleration
Velocity is rate of change of displacement. If velocity of a particle 18 variable, the rate of change of velocity is called acceleration. both velocity and acceleration are vectoi quantities."
(b) To ostermine the acceleration of a ball-
bearing rolling down a groove with the following. data given:-
distance moved
(cm)
10.
20 3.4 40 60 82.
time taken
(sec)
:3 4.6 6. 6.5 7.8 9
"A speed-came curve as plotted with the given data. The slopes of the curve drawn at P, Q, R, S, T corresponding to the time at the end of sec, 5 sec., 6 sec., 7.5 900 and 7.8 600., Tespectively are measured,
(111) Distance moved at the end or the centa
minute. $10
2 * 15 x 410 x 60)? Distance, moved at the end of the eleventh/ ainute
-11 - - x - - x (11 x 60)7
Distance moved during the eleventh
minute
10
602 = (112 - 102)
2.
∙15.
4 x 60 x 21 x SOLO Et.
(d) Maximum be light reached 2 miles
retardation
2 x 5280 It 32 ft./sec2
At the mix. height, velocity - 0 Let the initial valósity be u ft,
-2a
• 2 x (-32) x 2 x 5260
x 32 x 5280.
• 8 x 102.7
822 ft./380.
taken for the bullet to return to earth
utat?
The rod is balanced by a loop at 6, the
of gravity of the red. A piece of stone. known weight is hung on the opposite side
and adjust to ensure equilibrium.
The distance d m, of the stone from LE LE constant throughout the experiment. The distance of W from G is noted, di em. The stone is
immersed in a beaker of water and then in beaker or Liquid; and the balance is restored by moving towards Gy whence do and da em. ia recorded respectively.
Weight of stone in
Weight of stone in water
of stone in Liquid e
about G,
(2)
Mad
(3)
(2)
Subtract (2) from (2)
M2)d = W(dj
162
the lauld
Loss in weight of stone in liquid Loss in weight of stone in water/
Where
placement of the final position. which is 0.
Initial velocity
↑ -32 ft./sec2.
1 time taken
212.12
64 165
64/165
$1.6 sec.
4√165
The bullet must be fired with a velocity of 822 ft./sec,
51.4 seo. will elapse between the firing the gun and the return of the bullet to earth,
The slopes at the said points indicate instantaneous velocities there. Another She' velocitystam zrani „CAR-KNEVER
Questions for next week!
15. (a) Explain the terms |
Force, work, power
In what units are these quantitids measured: both in the matrio and British Bystems? (b) Given that I ounce 28.3 gram and that I in48
2.54 cm. 8 32.2 ft./800, determine
(11) the number of Idlowatta in 1 hers
(1 watt 107, erg/sec)
A can weighing half a top accelerates uniformly from rest, taking 30 sec. to attain & speed of 40 miles per hour. Negleating frictionless losses, calculate the horsepower of the engine when the speed is (1) 20 M and (15) 30
A simple pendulum or length 1 metre 13 vibrating with an amplitude of 309. What in the velocity of the pendulum bob at its Lowerest point?
these 4 msan value of
The graph to a straight line.
of the callwosaring sa uniform,
e) Initial
TWO BLEILAP bunkets, sach or maa 3 lb. are suspended from the two ends of a long,
of negligible mass passing over a less pulley and are at rest
the same level. A mass of 2 oz. is now plased
in one of the buckets. How long will it before the vertical distance between the bucketa is 6 ft.
A woode block of mas
smooth table da connected by
over a frictionless pulley at the
table to a mass of 10 gm
two portions of the card being
horisontal and vertical.
will the block slide along the tab the tension in the cord?