編號:

6633

年級:

中五 (F5)

科目:

物理 (Physics)

學校

檔案格式:

pdf

頁數:

27

檔名:

ysics La_Salle_College_F5_Physics_Mid_Year_Examination_2017_to_2018

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內容節錄：

General Instructions

This paper consists of THREE sections, Section A (Multiple Choice Questions), Section B (Short

Questions) and Section C (Long Questions). Section A carries 30 marks, Section B carries 28 marks and

Section C carries 42 marks.

2165 F5 LSC Sunny Chan Chun Sang

LA SALLE COLLEGE

Mid-Year Examination 2017 to 2018

8:15 am - 10:00 am (13 hours)

Instructions for Section A

Read carefully the instructions on the Answer Sheet. After the announcement of the start of the

examination, you should first write you Exam Number on the cover page of the question paper and

insert the information required in the spaces provided for "Subject", "Name", "Date", "Level", "Class"

and "Exam No." (in the boxes for "Class No.") on the Answer Sheet.

Answer all questions.

Answers to Section A should be marked on the Multiple-choice Answer Sheet while answers to

Sections B and C should be written in the spaces provided in the Question-Answer Book.

Exam Number

All questions carry equal marks.

When told to turn over the paper, check that all the questions are there. Look for the words 'END OF

SECTION A' after the last question.

Mark the answers of the Section A with an HB pencil on the Answer Sheet. You must mark the answers

clearly; otherwise you will lose marks if the answers cannot be captured.

No marks will be deducted for wrong answers.

Choose the best answer. You should mark only ONE answer for each question. If you mark more than

one answer, you will receive NO MARKS for that question.

F5 Physics Mid Year Exam 2017 to 2018 Section A

Page 1 of 11

Two point charges are fixed at the end of an insulating rod of length . The rod is placed in a uniform

electric field of field strength E in a vacuum. When the rod makes an angle with the field as shown in

Figure 27, the moment acting on the rod is

sin o clockwise

cos clockwise

QE sin & clockwise

QEl cos clockwise

2165 F5 LSC Sunny Chan Chun Sang

A. (1) and (2) only

B. (1) and (3) only

F5 Physics Mid Year Exam 2017 to 2018 Section A

Figure 28 shows a dipole consisting of two equal and opposite point charges separated by a distance 2d,

fixed along north-south direction. The line HOK runs along east-west direction, with O situated mid-way

between the charges. P₁, P₂ and P3 are three points on the line HOK. Which of the following statements

are correct?

(1) The electric field at all the marked points point towards south.

(2) The magnitude of the electric field strength at O is the largest among the marked points.

(3) If P30 = 2 P₂O, the magnitude of the electric field at P₂ is double that at P3.

C. (2) and (3) only

D. (1), (2) and (3)

Page 10 of 11

2165 F5 LSC Sunny Chan Chun Sang

A. (1) and (2) only

Two positive point charges are fixed on a vertical circle at positions shown in Figure 29. The direction of

the resultant electric field at the centre O of the circle acts along the vertical diameter MN. The ratio of

the charges 21 is equal to

B. (1) and (3) only

F5 Physics Mid Year Exam 2017 to 2018 Section A

A moving charged particle enters an electric field at P and its path inside the field is shown in Figure 30.

Every two neighbouring dotted lines have equal spacing and the same potential difference. (The dotted

lines represent some equipotential surfaces in the field.) If the only force acting on the charged particle is

electric force, which of the following must be correct?

(1) The particle carries negative charge.

(2) The particle experiences the same force at X and Y.

(3) The particle has larger kinetic energy at Y than at X.

End of Section A ***

C. (2) and (3) only

D. (1), (2) and (3)

Page 11 of 11

Instructions for Section B and Section C

After the announcement of the start of the examination,

you should first write your Exam Number in the space

provided on the cover page and every odd-numbered page

of this Question-Answer Book.

2165 F5 LSC Sunny Chan Chun Sang

LA SALLE COLLEGE

Mid-Year Examination 2017 to 2018

8:15 am - 10:00 am (13 hours)

Question-Answer Book

(Section B & Section C)

This paper must be answered in English

Refer to the general instruction on the cover page of the

Question Paper for Section A.

Answer ALL questions.

Write your answers of Section B and Section C in the

spaces provided in this Question-Answer Book.

Unless otherwise specified, numerical answers should be

either exact or correct to 3 significant figures.

Supplementary answer sheets will be supplied on request.

Write your Examination Number on each sheet and insert

them inside this book.

Take g = 9.81 m s2 and speed of light = 3 x 108 ms ¹¹.

Universal gas constant R = 8.31 J K¨¹ mol¹

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

Exam Number

Question No.

Question No.

Page 1 of 12

SECTION B: Short Questions (28 marks)

Answer ALL questions in this section and write your answers in the space provided.

Question No.

(a) Find v.

(b) If h= 3 cm,

2165 F5 LSC Sunny Chan Chun Sang

A uniform E-field is set up between two large parallel plates PQ. An electron, of mass 9.1 x 10³¹ kg and

charge -1.6 x 10-¹⁹ C, is projected with a velocity v at an angle from plate Q (Figure 1). The initial kinetic

energy of the electron is 10¹7 J. After some time, the electron returns to plate Q at a distance d from the

starting position. Neglect the effect of gravity.

(iii) find d.

(i) find the acceleration of the electron during the flight.

(ii) find the electric field strength between the plates.

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

Page 2 of 12

2165 F5 LSC Sunny Chan Chun Sang

A negatively charged cloud is 800 m above the surface of the Earth (Figure 2). For simplicity, the cloud

can be assumed to be planar with the negative charge uniformly distributed on its lower surface, and the

surface of earth can be assumed to be flat.

surface of the Earth

(+) rain droplet

(exaggerated)

(a) A positively charged rain droplet remains stationary midway in air in the field. If the radius of the

droplet is 0.5 mm and it carries +0.002 µC of charge, estimate the electric field strength between

the cloud and the ground. (Density of water = 1000 kg m³; 1 μC =

μC = 10° C)

(b) If the charged rain droplet in (a) suddenly loses its positive charge and then acquires a negative

charge of -0.002 µC by colliding with negative ions, estimate the speed of the droplet when it

reaches ground starting from rest at a height of 400 m, assuming both its charge and mass to remain

constant. Neglect air resistance.

If charges accumulate on the clouds, a lightning will occur when the electric field is large enough

to ionize the air so that it becomes conducting. Given that the minimum field strength for lightning

to occur is 8.0 x 105 V m¹ under wet air conditions, estimate the potential difference between the

cloud and the surface of the Earth when lightning starts.

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

Page 3 of 12

In the turntable arrangement shown in Figure 3, blocks A and B have masses 1 kg and 2 kg respectively.

Both their centres of mass are at a distance r 0.3 m from the rotational axis. The maximum friction

between A and B is 5 N and the turntable is smooth. The pulley is smooth and is of negligible mass.

2165 F5 LSC Sunny Chan Chun Sang

(a) The turntable is rotating at an angular speed of 4 rad s

(i) Find the tension of the string.

(ii) Find the frictional force acting on A by B. State also its direction,

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

(b) The angular speed of the turntable is increased gradually. Find its value when the two masses just

slide over each other.

Page 4 of 12

2165 F5 LSC Sunny Chan Chun Sang

(a) State the Newton's Law of universal gravitation.

(b) As shown in Figure 4, a rocket is launched from the surface of planet X and moves towards its

satellite Y under the influence of their gravitational forces only. The net gravitational force on the

rocket at C is zero.

positive direction

*** End of Section B

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

satellite Y

C is 2.5 x 105 km from the centre A of planet X and 6.25 x 105 km from the centre E of

Satellite Y. Find the ratio of the mass of planet X to that of satellite Y.

(ii) If the radius of Planet X is 3.2 times that of satellite Y, find a value for the ratio of the density

of planet X to the density of satellite Y.

Page 5 of 12

SECTION C: Long Questions (42 marks)

Answer ALL questions in this section and write your answers in the space provided.

Question No.

2165 F5 LSC Sunny Chan Chun Sang

In Figure 5a, a batter is going to hit a fast-moving baseball. The baseball is moving at 26 ms towards

the batter and is hit straight back along its incident path and moves at 35 ms with an angle of 40° to the

horizontal (Figure 5b). The mass of the baseball is 180 g and the time of impact between the bat and the

baseball is only 0.002 s.

(a) Calculate the impulse acting on the baseball by the bat during impact.

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

(b) Find the average force exerted on the baseball by the bat during impact.

Incident direction

(c) Assume the acceleration due to gravity is negligible; calculate the average acceleration of the

baseball during the time of impact.

Page 6 of 12

2165 F5 LSC Sunny Chan Chun Sang

(d) Is it a good approximation for us to ignore gravity for this calculation? Explain your answer.

(e) Ignore the height of the point of impact above the ground; calculate the horizontal range covered by

the baseball in the subsequent motion after the impact.

The batter hit the ball at a height of 1 m from the ground. The ball travels with a projectile path across

the baseball field, over the pitcher and the 2nd base to the outer-field (Figure 5c). An outer-field wall of

height 3 m and 120 m away from the batter is established at the boundary of the outer-field. If the ball

can fly over the outer-field wall in a hit, it is a home run. Otherwise if the ball hits the outer-field ground

or the wall, the outfielder can still catch the ball and send the ball back to base.

Outer-field

Figure 5c (not to scale)

(f) Find the time for the ball to travel to the wall which is 120 m away after the hit.

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

(g) Find the exact height where the ball reaches the distance of the wall. Will this hit become a home

run or will the ball hit the wall? Neglect air resistance.

Page 7 of 12

2165 F5 LSC Sunny Chan Chun Sang

Figure 6a shows a famous ride in amusement parks, the chair-o-plane. In the ride, chairs are connected to a

top disc by inextensible cables. When the ride starts, the top disc rotates about its centre and people sitting

on the chairs move in a horizontal circle.

(ii) Find the centripetal force acting on the system.

Figure 6b shows a simplified diagram of the chair-o-plane. Consider the boy and the chair as a single

system of total mass 200 kg.

(a) Draw a free-body diagram for the system. Show and label all forces acting on the system. (2 marks)

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

(b) If the system is circulating in a horizontal circle of radius r= 6 m and period 8 s.

(1) Find the angular velocity and the linear velocity of the system.

Page 8 of 12

Multiple Choice Questions (30 marks)

There are 30 questions in this section. Each question is followed by four suggested answers. Choose the BEST

answer from the four options.

Where necessary, take the acceleration due to gravity to be 9.81 ms2, take the speed of light in air to be

3×108 ms¹ and take the Universal gas constant R to be 8.31 J K™¹mol¹

A. Acceleration

A block is projected up a smooth incline with a certain velocity. After reaching the top of the incline, it

leaves the incline and continues to fly in the air as shown in Figure 1. Which of the following graphs best

shows how the magnitude of the acceleration of the block varies with time?

B. Acceleration

2165 F5 LSC Sunny Chan Chun Sang

Two particles P₁ and P₂ are at a distance of d m from each other,

and the line joining them makes an angle with the horizontal

as shown in Figure 3. P₁ is projected with a velocity of u ms¹

towards P₂ and P2 is released from rest simultaneously. Which

of the following statements is correct?

A. P₁ and P₂ will collide with each other after a time of

C. Acceleration

An object is projected at an angle to the horizontal in a vertical gravitational field. It follows a

parabolic path PQRS. P is the point of projection, Q, R and S are the positions of the object after

successive equal time intervals, and S is the highest point reached. Which of the following statements

concerning the displacements PQ, QR and RS is correct?

A. PQ, QR and RS are equal in magnitude.

PQ, QR and RS decrease at a constant rate.

PQ, QR and RS have equal horizontal component.

PQ, QR and RS have equal vertical component.

P₁ and P₂ will collide with each other after a time of

D. P₁ and P₂ will not collide with each other.

P₁ and P₂ will collide with each other after a time of

F5 Physics Mid Year Exam 2017 to 2018 Section A

D. Acceleration

Page 2 of 11

2165 F5 LSC Sunny Chan Chun Sang

(iii) Find the tension in the cable and the angle that the cable makes with the vertical. (3 marks)

If the size of the disc is increased so that the boy rotates around the central axis X-Y with a radius of

8 m and the period of rotation is still 8 s, find the tension in the cable and the angle that the cable

makes with the vertical.

(d) (i) In part (b), Explain how the angle would change when the top disc rotates in a higher

angular speed.

(ii) In part (b), describe, if any, the change in the value of the angle if

(1) the boy is replaced by a heavier man, and

(2) the length of the cable is increased.

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

Page 9 of 12

2165 F5 LSC Sunny Chan Chun Sang

(a) Ethan is pumping air slowly into a basketball (Figure 7a). For each stroke, 500 cm³ of air, at 100

kPa is pumped into the ball. Initially, the air pressure inside the basketball is 100 kPa. Throughout

the whole process, the volume of the basketball is 7000 cm³ and the air temperature is kept at 20 °C.

(i) Find the number of moles of air pumped into the basketball in each stroke.

(ii) If the standard air pressure inside the basketball has to exceed 130 kPa, at least how many

complete strokes are needed?

(iii) The cross-sectional area of the air column in the pump is 15 cm². Estimate the force required

to push the last stroke of the pump. Assume the average air pressure inside the basketball

during this stroke is 130 kPa.

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

Page 10 of 12

2165 F5 LSC Sunny Chan Chun Sang

Inside a vacuum box, a cylindrical container with a smooth piston traps some ideal monatomic gas.

The mass of the piston is 6 kg. The height of the gas column is 15 cm. The base area of the

container is 300 cm². The temperature of the gas is 300 K.

(i) Find the number of moles of gas inside the container.

The gas is now heated to 400 K at constant pressure.

(ii) Find the new height of the gas column.

(iii) Find the increase in internal energy of the gas inside.

(iii) By what factor has the rims speed of the gas molecules increased?

*** End of Section C

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

Page 11 of 12

2165 F5 LSC Sunny Chan Chun Sang

Supplementary Answer Sheet

F5 Physics Mid-year Exam 2017 to 2018 Section B and Section C

Page 12 of 12

1. (a) Given that Ek = mv² = 10-17J.

V=4.688x106 = 4.69x106 ms-¹

(ii) Since qE = ma,

(b) (i) Applying v²-u² = 2as in vertical direction,

2017-2018 F.5 Physics Mid-Year Examination Answers

a = (4.688 x 106 x sin45°) ²/(2 x 0.03) = 1.832 x 10¹4

= 1.83x1014 ms-2

2165 F5 LSC Sunny Chan Chun Sang

(iii) We know that t = 2vsin45°/a-3.619 x 10-8 s.

So d = vcos45°t = 0.12m.

2. (a) Weight of the droplet = mg = (volume x density) x g

E = (9.1 x 103¹)( 1.83x10¹4)/(1.6x10-1⁹)

= 1.04x10³ NC-¹. (1040 V/m)

T(0.5 x 10-³)³ x 1000 x 9.81

(b) Net force = mg+qE

=(5.236x107) x 9.81 = 5.1365 x 10-6N

Upward force = qE

qE5.1365 x 10-6 N

E = 5.1365x10-6 / 0.002 x10-6 = 2570 NC-¹

La Salle College

a = F/m = 1.027x105 /5.236 x 107 = 19.61ms-²

By v² = u²+2as

(4690000 m/s)

v=√ 2x19.61x400 = 125ms-¹

= 2 x 5.1365 x 10-6 N = 1.027 x 10¹5 N (downward)

3. (a) (i) Consider the whole system,

= 8.0 x 105 x 800 V = 6.4x108 V

2 T = (MA+MB) ro² = (1 + 2) (0.3) (4)²

So, T= 7.2 N

(ii) For A, T-f= MARC² = 4.8 N.

So f = 2.4 N.

It points away from the centre.

(b) When f = fmax = 5 N, the two masses just slide over each other.

Equation for circular motion of A and B,

T-fmax = mar@²max

T+fmax = mero², ----(2)

Eliminating T by (2)-(1), we get

10 (MBMA) ro²ma

5.77 rad s-1

4. (a) Every particle in the universe attracts every other particle with a gravitational force

that is directly proportional to the product of their masses and inversely proportional

to the square of the distance between them.

(b) At point C, the net gravitational force = 0, Fx = Fy

(c) Density = p=

(2.5 X105)²

Bankerde Lice www.

(6.25 X105)²

Mx: My = 4:25 (or 0.16: 1 or 1: 6.25)

5. (a) Impulse = mv-mu

=0.18[35-(-26)]

2165 F5 LSC Sunny Chan Chun Sang

(6.25 X105)2

Px: Py = 0.00488:1 (or 5: 1024 or 1: 205)

10.98 11.0 Ns-¹

(c) By Newton's Second Law,

a = F/m = 5500/0.18 = 3.06 x 104 ms-2 (30600 ms-²)

Or =5490 /0.18 = 3.05 x 104 ms² (30500 ms ²)

(d) It is a good approximation for us to ignore gravity

as g (9.81 ms 2) is much smaller than the acceleration calculated above.

u² sin20 35² sin(2x40)

= 122.97 m 123 m (3 sig, fig)

(f) From (e), we know that the ball will either hit on the wall or over the wall but will not

land on the outer-field.

t = Time to reach the wall 120 m away

120 35 cos 40° = 4.48 sec

(g) S = ut +

At t = 4.48 sec, height of the ball above the ground

h = 1 + 35 sin 40° (4.48) + (-9.81)(4.48)²

= 3.34 m > 3 m

It can pass over the wall → It is a home run.

6. (a) Correct force direction and label

(iii) T sin

= 0.785 rad s-¹

v=rw = (6)(0.785)

= 4.71 m s¹

2165 F5 LSC Sunny Chan Chun Sang

- weight, mg

= Fc = 740 N

= mg = 1962 N

(1)÷(2)→ tan 0 = 740 / 1962

T sin 20.7° = 740 N

(200)(4.71)²

(c) Angular speed w does not change = 0.785 rad s-¹

v=rw = (8)(0.785)

= 6.28 m s-¹

tan 986/1962

T sin 26.7° = 986 N

mv² (200)(6.28)2

(d) (i) The angle increases.

Centripetal force increases with the angular speed of the system.

As Fc =T sin 0,8 increases when Fc increases.

The angle & unchanged. (tano = rw²/g → 0 is independent of m)

ii) The angle increases. (tane = and r I sin 0 g/w² = l cos 0)

7. (a) (i) n=pV/(RT)

(ii) For 130 kPa, extra no. of moles of gas needed is

n = (130 x 10³ - 100 x 10³) (7000 x 106)/(8.31 x (20 +273))

= 0.0862 mol.

No. of strokes is 0.0862/0.0205 = 4.2

So at least 5 strokes are needed.

(iii) Ap = p - po = 30 x 10³ Pa, where po is the atmospheric pressure.

= Ap A=(30x10³)(15x10-4)

(b) (i) p = mg/A = (6)(9.81)/(300x 10-4)

n =pV/(RT) = (1962) (300 x 15 x 106)/(8.31 x 300)

= 0.003542 = 0.00354 mol. (3 sig. fig)

(ii) By V₁/T₁= V₂/T2, the new height is

= (100 x 10³) (500 x 106)/(8.31 x (20+273))

= 0.02054 = 0.0205 mol. (3 sig. fig)

(iii) AE = nRAT =

2165 F5 LSC Sunny Chan Chun Sang

(iv) As vms oc E or o T

(0.003542)(8.31)(100)

= 4.4145 J= 4.41J. (3 sig. fig)

Vrms is increased by a factor of

Section A Answers

A marble is released from rest from the highest point of the roof of a house as shown in Figure 4. At

what angle with the horizontal (0) does the marble hit the ground?

2165 F5 LSC Sunny Chan Chun Sang

Two identical balls P and Q are projected from the same position with the same speed u as shown in

Figure 5. P is projected with an angle above the horizontal while Q is projected with the same angle

below the horizontal. Suppose they land on the same level. What is the distance between their landing

F5 Physics Mid Year Exam 2017 to 2018 Section A

An object is initially placed on a horizontal smooth platform. It explodes and splits into two parts A and

B of mass m and 2m respectively in the horizontal direction (Figure 6). The parts finally land on the same

level. The horizontal distances of the landing positions of A and B from the platform are dĄ and de

respectively. Find the ratio dд: dB.

Page 3 of 11

A bomber flying horizontally with a constant velocity u releases a bomb which is initially at rest relative

to the bomber. Just before hitting the ground, the bomb acquires a speed v. What is the time of flight of

the bomb? (Neglect air resistance.)

2165 F5 LSC Sunny Chan Chun Sang

A. (1) only

(1) Net vertical force acting on the particle is 2.94 N.

Net horizontal force acting on the particle is 4 N.

(3) Tension in the string is 4.96 N.

B. (2) only

B. √√rg sine

F5 Physics Mid Year Exam 2017 to 2018 Section A

√√₁²

A particle of mass 0.3 kg is attached to one end of a string. The other end of the string is fixed to the

ceiling (Figure 8). The particle swings in a horizontal circle of radius 0.52 m forming a conical pendulum

as shown in Figure 8. If the period of the conical pendulum is 1.24 s, which of the following statements

is/are correct?

C. (1) and (3) only

C. √rg cos

A marble rotates inside a conical container as shown in Figure 9. The wall of the container is smooth.

The radius of the circular path followed by the marble is r. What is the velocity of the marble?

(g: acceleration due to gravity)

A. √rg tan

D. (2) and (3) only

D. √rg cot

Page 4 of 11

A car travels round a bend on a banked road. Which of the following statements is/are correct?

(1) The weight of the car is tilted and provides part of the centripetal force.

The centripetal force required is reduced when the road is banked.

(3) The normal reaction on the car from the road is increased when the road is banked.

A. (1) only

A. 1.2 rad s

2165 F5 LSC Sunny Chan Chun Sang

B. (3) only

Two wheels P and Q are connected by a belt (Figure 11). The axle of P is driven by a motor (not shown)

and the wheels are rotated. The belt does not slip on the wheels. The diameter of P is 5 cm and that of Q

is 12 cm. If the angular velocity of P is 0.50 rad s¹ what is the angular velocity of Q?

B. 0.50 rad s¹

C. (1) and (3) only

SLAGERIMERJAJ TAKEG

F5 Physics Mid Year Exam 2017 to 2018 Section A

C. 0.21 rad s¹

A small sphere is attached to a light spring with one end fixed to a nail at the centre of a smooth

horizontal turntable (Figure 12). The tension in the spring is directly proportional to its extension under

stretching and the natural length of the spring with no tension is . The small sphere is set to rotate

together with the turntable by a motor. When the angular speed of the turntable is the length of the

spring becomes 2. When the angular speed is increased to w', the length of the spring becomes 3£. Find

axle rotated by a motor

D. (2) and (3) only

D. 0.12 rad s

Page 5 of 11

A. 1.40 hours

P and Q are two identical uniform spheres of radius r and made of a material of density p, placed in

contact as shown in Figure 13a. They attract each other with a gravitational force f. R and S are another

two identical uniform spheres of radius 2r made of a material of density 2p, also placed in contact, as

shown in Figure 13b. What is the gravitational attraction between R and S?

A. (2) only

2165 F5 LSC Sunny Chan Chun Sang

14. The gravitational field strength at the surface of a uniform spherical planet of radius 6800 km is 12 Nkg¹.

It has a satellite moving in a circular orbit of radius 8 000 km. Calculate the period of this satellite.

is/are correct?

(1) The orbiting speed remains unchanged.

(2) The period becomes

(3) The centripetal acceleration becomes

B. 1.68 hours

15. A satellite moving around the Earth in a circular orbit of radius R has a period and centripetal

acceleration a. If it now moves in another circular orbit of radius which of the following statements

B. (3) only

F5 Physics Mid Year Exam 2017 to 2018 Section A

C. 12.0 hours

16. Suppose a small meteorite falls directly towards the Earths centre from space. Which of the following

graphs best shows how its speed v changes with time t? Neglect air resistance.

C. (1) and (2) only

D. 13.6 hours

D. (1) and (3) only

Page 6 of 11

A satellite travels in a circular orbit of radius r round the Earth (Figure 17). Let the radius of the Earth be

R and the gravitational field strength on the surface of the Earth is g. Which of the following gives the

velocity of the satellite?

A. √√Rg

Pressure / Pa

A. 2.40 x 105 pa

2165 F5 LSC Sunny Chan Chun Sang

An ideal gas is contained in two metal cylinders P and Q connected by a tap which is initially closed

(Figure 18). The volume and pressure of the gas in the cylinders are as follows

Volume / m³

B. 3.00 x 105 pa

When the tap connecting the two cylinders is opened, what will be the final pressure in the vessel? You

may assume that the temperature remains constant.

F5 Physics Mid Year Exam 2017 to 2018 Section A

A fixed mass of ideal gas undergoes changes from state a to state c via state b, as shown by the graph of

pressure P against volume in Figure 19. Which graph best shows how the absolute temperature T of the

gas varies with its volume ?

C. 3.33 x 105 Pa

D. 3.75 x 105 pa

Page 7 of 11

20. An ideal gas exerts a pressure 1.0 x 105 Pa when its temperature is 400 K and the number of molecules

present in unit volume is N. Another sample of the same gas exerts a pressure of 0.5 x 105 Pa when its

temperature is 300 K. How many molecules are present in unit volume of this second sample?

2165 F5 LSC Sunny Chan Chun Sang

A. (1) only

A fixed mass ideal gas undergoes a process from A to B during which its pressure p and volume V change

as shown in the p-V graph in Figure 21. If the r.m.s. speed of the molecules at point A is c, find the r.m.s

speed of the molecules at point B in terms of c.

B. (2) only

F5 Physics Mid Year Exam 2017 to 2018 Section A

22. The absolute temperature of a fixed mass of ideal gas rises from 7 to 27 under constant pressure. Which

of the following is/are correct?

(1) The r.m.s. speed of the gas molecules is doubled.

(2) The volume of the gas is doubled.

(3) The frequency of collision on a container wall is reduced by a factor of √2.

C. (1) and (3) only

Under standard atmospheric pressure (1.01×105 Pa ), air has a density of 1.2 kg m³ at 20 °C. Calculate

the root mean square speed of air molecules at 100 °C.

C. 1120 ms™¹

D. (2) and (3) only

D. 2510 ms¹

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An ideal gas in a container is compressed by a movable piston. However, some gas leaks out slowly from

the container during the process. The graph in Figure 24 shows the variation of the volume V against the

pressure p of the gas during the process. If the temperature of the gas rises from 25 °C to 40 °C during

the process, find the percentage of the original mass of the gas that leaked out.

2165 F5 LSC Sunny Chan Chun Sang

25. Two point charges +q and +2q are separated by a distance d. A neutral point exists on the line joining

them. How far is the point from +q?

F5 Physics Mid Year Exam 2017 to 2018 Section A

In Figure 26, the two positive point charges are of equal magnitude. A negative point charge is placed at

P. Which of the following figures best describes the direction of the electric force acting on P?

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