Question 1

1 mark

A long, straight vertical wire carries a steady electric current

I

directed vertically upwards. Point

X

is located at a horizontal distance

d

due North of the wire. In which direction is the magnetic field produced by the current at point

X

?

A.Vertically upwards
B.Vertically downwards
C.Due North
D.Due West
E.Due East

Answer: D

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Question 2

1 mark

An ideal step-up transformer at a power station has a turns ratio of

1 : 20

(primary to secondary). The transformer's primary coil receives a current of

200\,\text{A}

at a voltage of

500\,\text{V}

from the station's generator. The output of this transformer is connected to a transmission cable with a total resistance of

50\,\Omega

. At the far end of the cable, the electrical power is delivered to a step-down transformer that is

80\%

efficient. What is the power output from this step-down transformer?

A. $72\,\text{kW}$
B. $75\,\text{kW}$
C. $76\,\text{kW}$
D. $80\,\text{kW}$
E. $95\,\text{kW}$

Answer: C

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Question 3

1 mark

A block of mass

5.0\text{ kg}

is being pulled vertically upwards by a light string. The string exerts a constant upward tension of

65\text{ N}

on the block. At a certain instant, the block is moving upwards and experiences a constant air resistance (drag) force of

3.0\text{ N}

.

What is the magnitude of the acceleration of the block at this instant?
(gravitational field strength

g = 10\text{ N kg}^{-1}

)

A. $2.4\text{ m s}^{-2}$
B. $3.0\text{ m s}^{-2}$
C. $3.6\text{ m s}^{-2}$
D. $12.4\text{ m s}^{-2}$
E. $13.0\text{ m s}^{-2}$

Answer: A

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Question 4

1 mark

A light spring

S_1

with a spring constant

k_1 = 100\,\text{N m}^{-1}

and a second light spring

S_2

with a spring constant

k_2 = 200\,\text{N m}^{-1}

are suspended vertically from a ceiling. The natural length of

S_2

is

0.10\,\text{m}

shorter than that of

S_1

. A light, rigid horizontal plate is attached to the bottom of

S_1

, and initially, the lower end of

S_2

is positioned exactly

0.10\,\text{m}

above this plate.

When a weight

W = 50\,\text{N}

is gradually added to the plate,

S_1

extends until the plate makes contact with

S_2

, after which both springs extend together in parallel.

Assuming both springs remain within their limit of proportionality, what is the total elastic potential energy stored in the system when the weight is in equilibrium?

A. $4.0\,\text{J}$
B. $4.2\,\text{J}$
C. $4.5\,\text{J}$
D. $5.8\,\text{J}$
E. $8.5\,\text{J}$

Answer: C

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Question 5

1 mark

Two blocks,

P

and

Q

, with masses of

3.0\,\text{kg}

and

2.0\,\text{kg}

respectively, are in contact on a smooth horizontal surface. A constant horizontal force of

15\,\text{N}

is applied to block

P

, pushing it towards block

Q

.

What is the magnitude of the force that block

P

exerts on block

Q

?

A. $3.0\,\text{N}$
B. $6.0\,\text{N}$
C. $7.5\,\text{N}$
D. $9.0\,\text{N}$
E. $15\,\text{N}$

Answer: B

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Question 6

1 mark

A skydiver of total mass

90\,\text{kg}

is falling vertically. At a certain instant after opening their parachute, the air resistance acting on the skydiver and parachute is

1170\,\text{N}

. What is the magnitude and direction of the skydiver's acceleration at this instant?
(The gravitational field strength

g

is

10\,\text{N kg}^{-1}

.)

A. $3.0\,\text{m s}^{-2}$ downwards
B. $3.0\,\text{m s}^{-2}$ upwards
C. $13\,\text{m s}^{-2}$ upwards
D. $10\,\text{m s}^{-2}$ downwards
E. $23\,\text{m s}^{-2}$ upwards

Answer: B

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Question 7

1 mark

A ball of mass

0.40\,\text{kg}

is moving horizontally at a speed of

5.0\,\text{m s}^{-1}

when it strikes a vertical wall. The ball rebounds directly backwards in the opposite direction. During the collision,

75\%

of the ball's initial kinetic energy is lost. The ball is in contact with the wall for

0.050\,\text{s}

. What is the magnitude of the average resultant force acting on the ball while it is in contact with the wall? (Assume that no other external forces act on the ball during the collision.)

A. $20\,\text{N}$
B. $40\,\text{N}$
C. $50\,\text{N}$
D. $60\,\text{N}$
E. $80\,\text{N}$

Answer: D

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Question 8

1 mark

A tall, narrow glass cylinder is filled with a liquid that is initially at a uniform temperature of

20^\circ\text{C}

. The density of the liquid is known to decrease as its temperature increases. Two experiments are conducted to observe the behavior of the liquid:

Experiment 1: A heating element at the bottom of the cylinder is switched on to warm the liquid locally to

40^\circ\text{C}

.
Experiment 2: An identical heating element at the top of the cylinder is switched on to warm the liquid locally to

40^\circ\text{C}

.

Which of the following statements correctly describes the resulting fluid flow in these two experiments?

A.In Experiment 1, a convection current is established because the heated liquid at the bottom becomes less dense and rises. In Experiment 2, no significant convection occurs because the heated liquid at the top remains at the top.
B.In Experiment 1, no significant convection occurs because the heated liquid at the bottom becomes more dense and remains there. In Experiment 2, a convection current is established because the heated liquid at the top becomes more dense and sinks.
C.In Experiment 1, a convection current is established because the heated liquid at the bottom becomes less dense and rises. In Experiment 2, a convection current is also established because the heated liquid at the top becomes more dense and sinks.
D.In both experiments, convection currents are established throughout the entire volume of the liquid because any localized change in temperature causes the liquid to circulate.
E.In Experiment 1, no significant convection occurs. In Experiment 2, a convection current is established because the heated liquid at the top becomes less dense and sinks to the bottom.

Answer: A

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Question 9

1 mark

Two solid copper spheres,

X

and

Y

, are placed in a vacuum chamber. Sphere

X

has radius

r

and a dull black surface. Sphere

Y

has radius

3r

and a shiny polished surface. At any given temperature, the rate of thermal radiation emission per unit surface area for the dull black surface is

10

times that of the shiny polished surface. Both spheres are initially at the same high temperature

T

, and the walls of the vacuum chamber are maintained at

0\, \text{K}

.

Let

P_X

and

P_Y

be the initial rates of thermal energy emission from the surfaces of

X

and

Y

respectively.

Let

R_X

and

R_Y

be the initial rates of temperature decrease for

X

and

Y

respectively.

Which of the following correctly identifies the ratios

\frac{P_X}{P_Y}

and

\frac{R_X}{R_Y}

?

A. $\frac{P_X}{P_Y} = \frac{10}{9}$ and $\frac{R_X}{R_Y} = \frac{10}{3}$
B. $\frac{P_X}{P_Y} = \frac{10}{9}$ and $\frac{R_X}{R_Y} = 10$
C. $\frac{P_X}{P_Y} = \frac{10}{9}$ and $\frac{R_X}{R_Y} = 30$
D. $\frac{P_X}{P_Y} = 10$ and $\frac{R_X}{R_Y} = 30$
E. $\frac{P_X}{P_Y} = 10$ and $\frac{R_X}{R_Y} = 270$

Answer: C

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Question 10

1 mark

A substance has a density of

\rho_{\text{L}} = 1350\,\text{kg m}^{-3}

in its liquid state. When the substance evaporates at a constant pressure, its density decreases to

\rho_{\text{G}} = 0.050\,\text{kg m}^{-3}

. In a simple particle model of the states of matter, each particle is assumed to occupy a cubic volume

V_{\text{p}} = d^3

, where

d

is the average distance between the centers of adjacent particles. Using this model, what is the ratio of the average distance between particles in the gas to that in the liquid,

\frac{d_{\text{G}}}{d_{\text{L}}}

?

A. $3$
B. $27$
C. $30$
D. $300$
E. $27000$

Answer: C

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Question 11

1 mark

A diver is at a depth of

4.0\,\text{m}

in a fresh-water lake. The density of the water is

1000\,\text{kg m}^{-3}

, the gravitational field strength

g

is

10\,\text{N kg}^{-1}

, and the atmospheric pressure at the surface is

1.0 \times 10^5\,\text{Pa}

. The diver's watch has a flat face with an area of

5.0\,\text{cm}^2

. What is the magnitude of the total force exerted by the water and the atmosphere on the outer face of the watch?

A. $20\,\text{N}$
B. $50\,\text{N}$
C. $70\,\text{N}$
D. $200\,\text{N}$
E. $700\,\text{N}$

Answer: C

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Question 12

1 mark

A stationary ship uses a sonar system to detect a shoal of fish and the seabed. The system emits sound waves with a frequency of

25\text{ kHz}

and a wavelength of

6.0\text{ cm}

in the water. The ship is positioned

900\text{ m}

directly above the seabed. A single pulse is emitted; the echo from the shoal of fish is detected first, and then the echo from the seabed is detected

0.40\text{ s}

later. What is the depth of the shoal of fish below the ship, and is the signal audible to humans?

A.depth: $300\text{ m}$ ; audibility: audible to humans
B.depth: $300\text{ m}$ ; audibility: not audible to humans
C.depth: $600\text{ m}$ ; audibility: audible to humans
D.depth: $600\text{ m}$ ; audibility: not audible to humans
E.depth: $1200\text{ m}$ ; audibility: not audible to humans

Answer: D

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Question 13

1 mark

Two electromagnetic waves,

P

and

Q

, travel through a vacuum. Wave

P

has a frequency

f_P = 2.5 \times 10^{13}\,\text{Hz}

and is the type of radiation predominantly emitted by objects at room temperature (

300\,\text{K}

). Wave

Q

has a wavelength

\lambda_Q

such that the ratio of the wavelength of

P

to the wavelength of

Q

is:

\frac{\lambda_P}{\lambda_Q} = 2.5 \times 10^5

The speed of light in a vacuum is

c = 3.0 \times 10^8\,\text{m}\,\text{s}^{-1}

. Which row in the table correctly identifies the speed of wave

Q

in a vacuum, the likely nature of wave

Q

, and a common application or hazard associated with it?

A.speed of $Q$ : $3.0 \times 10^8\,\text{m}\,\text{s}^{-1}$ ; nature: X-ray; application/hazard: used for medical imaging of bones
B.speed of $Q$ : $3.0 \times 10^8\,\text{m}\,\text{s}^{-1}$ ; nature: radio wave; application/hazard: used for local radio broadcasting
C.speed of $Q$ : $1.2 \times 10^3\,\text{m}\,\text{s}^{-1}$ ; nature: X-ray; application/hazard: used for medical imaging of bones
D.speed of $Q$ : $3.0 \times 10^8\,\text{m}\,\text{s}^{-1}$ ; nature: gamma ray; application/hazard: used for medical sterilization
E.speed of $Q$ : $3.0 \times 10^8\,\text{m}\,\text{s}^{-1}$ ; nature: ultraviolet; application/hazard: causes skin cancer

Answer: A

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Question 14

1 mark

An unstable nucleus

^{A}_{Z}X

undergoes a decay process consisting of the emission of exactly one alpha (

\alpha

) particle and exactly two beta-minus (

\beta^-

) particles. Which of the following correctly describes the atomic number and mass number of the resulting nucleus?

A.atomic number: $Z$ ; mass number: $A - 4$
B.atomic number: $Z - 2$ ; mass number: $A - 4$
C.atomic number: $Z + 2$ ; mass number: $A - 4$
D.atomic number: $Z - 4$ ; mass number: $A - 4$
E.atomic number: $Z$ ; mass number: $A - 2$

Answer: A

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Question 15

1 mark

A glass rod is initially neutral. It is rubbed with a silk cloth, and as a result,

4.0 \times 10^{10}

electrons are transferred from the rod to the cloth. What is the resulting charge on the glass rod? (The elementary charge is

e = 1.6 \times 10^{-19}\,\text{C}

).

A. $+6.4 \times 10^{-9}\,\text{C}$
B. $-6.4 \times 10^{-9}\,\text{C}$
C. $+6.4 \times 10^{-29}\,\text{C}$
D. $-6.4 \times 10^{-29}\,\text{C}$
E. $0\,\text{C}$

Answer: A

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ESAT Mock Physics Esat-physics-bank-1

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15