# Physics 2012 DSE

2075 Words Sep 19th, 2013 9 Pages

FOR MARKERS’ USE ONLY

May 4, 2012

HONG KONG EXAMINATIONS AND ASSESSMENT AUTHORITY
2012 年香港中學文憑考試
HONG KONG DIPLOMA OF SECONDARY EDUCATION EXAMINATION 2012

PHYSICS HKDSE PAPER 1B

This marking scheme has been prepared by the Hong Kong Examinations and Assessment Authority for markers’ reference. The Authority has no objection to markers sharing it, after the completion of marking, with colleagues who are teaching the subject.
However, under no circumstances should it be given
Because energy loss by the steam is also gained by the surroundings including the air/the jug (usually metallic) that holds milk.

1
)
V
4
4 p1 ( π × (0.8) 3 ) = (1.01 × 10 5 Pa )( π × (1.0) 3 )
3
3 p1V1 = p2V2 (Or p ∝

5

p1 = 1.97 × 10 Pa

1M correct eqn. or with sub.

1A

3

= 45600 J 1 A
1M
1A

2

1A
1A
2

1M

1A correct answer, accept 2 sig. fig.
[Accept without

4 π] 3

1A

2

(Accept 1.97 × 105 Pa to 2.00 × 105 Pa)
(b)

3.

(a)

Volume increases as bubble rises but the speed / k.e.
1A speed / k.e. of molecules of gas molecules remains unchanged unchanged therefore frequency of collision of molecules on
1A frequency of collision on inner bubble’s inner surface decreases, gas pressure decreases. surface/wall decreases AND pressure decreases

1A

(i)

1A

Friction f between the tyres and the road. mv 2 f = r 8000 N =

(1200 kg)v 2
45 m

1A Friction
1M correct eqn. or with sub.

2
1A

1M

v = 17.3 m s −1
(Accept 17.0 to 17.4 m s–1)
(ii)

(b)

1A

3

Smaller
For the same f, v2 ∝ r, r decreases, v decreases.

1A
1A

2

(Max) friction / coefficient of friction reduced,
Not enough to provide the centripetal force / acceleration required for circular motion.
Or Tracking or allowed speed lowered.

2012-DSE-PHY 1B–3

FOR MARKERS’ USE ONLY

1A
1A

2

FOR MARKERS’ USE ONLY
Marks

4.

(a)

(i)

v = u + at

1M correct sub. into correct eqn.

= 60 + (– 4)5

= 40 m s –1
(ii)

1M
1A

2

v / m s –1

60
40

A