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WAEC: PHYSICS 2015 Physics WAEC (WASSCE) Past Questions 2015 Physics WAEC (WASSCE) Essay Past Questions (Paper 2)
Lesson 11, Topic 1
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2015 Physics WAEC (WASSCE) Essay Past Questions (Paper 2)

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Content:

  • 2015 Physics WAEC (WASSCE) Essay Past Questions (Paper 2)
  • SECTION A (1 – 7) – Will comprise seven short-structured questions. Candidates will be required to answer any five questions for a total of 15 marks.
  • SECTION B (8 – 12) – Will comprise five essay questions out of which candidates will be required to answer any three for 45 marks.
  • Duration – 1½ hours

Go to Question

1   2    3    4    5    6    7    8    9    10    11    12

SECTION A (1 – 7)

Answer any five (5)

Question 1:

(a) What is a projectile?

(b) Give the reason why the horizontal component of the velocity of a projectile remains the same at every point of its flight.

View Answers

Question 2:

A body is projected at an angle of 30° to the horizontal with a velocity of 150 ms-1. Calculate the time it takes to reach the greatest height.

[Take g = 10 ms-2 and neglect air resistance]

View Answers

Question 3:

A wire of length 2.00 m and radius 1.0 mm is stretched by 25.0 mm on the application of a force of 103 N. Calculate the Young’s modulus for the wire.

View Answers

Question 4:

State three ways of increasing the rate of cooling of a cup of hot tea.

View Answers

Question 5:

(a) What is doping in a semi conductor?

(b) Draw the symbol for OR gate.

View Answers

Question 6:

Screenshot 2025 02 10 at 08.27.24

The circuit above consists of an a.c. voltage input, a diode, a resistor and a voltmeter.

(a) Identify the circuit.

(b) Draw the waveform for the output voltage.

View Answers

Question 7:

(a) Write the De Broglie equation.

(b) Explain the significance of the equation.

View Answers

SECTION B (8 – 12)

Answer any three (3)

Question 8:

(a) (i) Define uniform acceleration.

(ii) Write an equation that relates linear velocity, angular velocity and radius
of path in circular motion.

(b) Two forces 30 N and 40 N act at right angles to each other. Determine by scale drawing, the magnitude and direction of the resultant force, using a scale of 1 cm to 5 N.

(c) Explain why ships are usually refilled with sand and water after they have been emptied of their cargo.

(d) A crate of drinks of mass 20 kg is placed on a plane inclined at 30° to the horizontal. If the crate slides down with a constant speed, calculate the:

(i) co-efficient of kinetic friction;

(ii) magnitude of the frictional force acting on the crate. [ g = 10 ms-2]

View Answers

Question 9:

(a) Define specific latent heat of vaporization.

(b) (i) What are renewable energy sources?

(ii) List four renewable energy sources.

(c) Explain why tomatoes keep longer when kept in a moist jute bag in a clay pot.

(d) (i) A box has a volume of 0.28 m3 and is 70% filled with iron fillings at 25ºC. Calculate the total mass of the iron fillings

[Density of iron = 8.00 × 103 Kgm-3, specific latent heat of fusion of iron = 1.38 × 105JKg-1, specific heat capacity of iron = 460 JKg-1K-1, melting point of iron = 1500ºC]

(ii) A box has a volume of 0.28m3 and is 70% filled with iron fillings at 25ºC. Calculate the energy required to melt 10% of the iron fillings.

[Density of iron = 8.00 × 103 Kgm-3, specific latent heat of fusion of iron = 1.38 × 105 JKg-1, specific heat capacity of iron = 460 JKg-1K-1, melting point of iron = 1500ºC]

View Answers

Question 10:

(a)(i) what is resonance?

(ii) State two examples of resonance.

(iii) Differentiate between loudness and intensity of sound.

(b) When a ray is refracted through a rectangular glass prism, which of the following properties of the ray will change? Wavelength, frequency, and speed.

(c)

Screenshot 2025 02 10 at 13.38.25

(i) Copy the diagram above in your answer booklet.

(iii) On the copied diagram, sketch the pattern of the waves immediately after passing through the opening.

(d) A diverging lens of focal length 18.0 in is used to view a shark that is 90.0 in away from the lens. If the image formed is 1.0 m long, calculate the:

(i) image distance;
(ii) length of the shark.

View Answers

Question 11:

(a) Define: (i) the coulomb; (ii) resistance.

(b) State the three effects of an electric current.

(c) State the standard international colour convention for the insulating material covering the following electrical wires in a three-pin plug: (i) live; (ii) neutral; (iii) earth.

(d)

Screenshot 2025 02 10 at 14.33.471

A watermelon of mass 5.0 kg is suspended on a uniform rod of mass 4.0 kg and 4.0 m in long as illustrated in the diagram above. If the rod is in equilibrium by the action of the force between the charges +q and -q, calculate the:

(i) anti-clockwise moment;
(ii) value of q

[ g = 10 ms-2]

View Answers

Question 12:

(a) Define nucleon number

(b) A radioactive isotope of Americium (Am – 241) decays into a nucleus of Neptunium (Np – 237) and an alpha (α) particle as shown in the nuclear equation below.

\( \scriptsize ^{241}_{95}Am\: \to \: ^{237}_{c}Np \: + \: ^b_a \alpha\)

(i) State the number of neutrons in the nucleus of Americium – 241.

(ii) Determine the values of a, b and c.

(c)(i) Why are γ-rays not deflected by electromagnetic field?

(ii) State two properties of gamma rays that make them suitable for sterilizing medical equipment.

(d) A sample of radioactive substance was found to be left with h of its initial count rate after 110 years. Calculate its decay constant.

View Answers

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Question 1

(a) What is a projectile?

Answer

Any object thrown into the air and allowed to fall freely under the influence of gravity is called a projectile.

The trajectory, or curved motion, or the path taken or described by a projectile while in the air is a trajectory.

A projectile motion is a curved motion described by a falling object in the air.

 

(b) Give the reason why the horizontal component of the velocity of a projectile remains the same at every point of its flight.

Answer

There is only one force acting on the object in the air, that is due to gravity, acting downwards. Since no force is acting in a horizontal direction therefore the magnitude of velocity and angle remain constant.

Mathematically,

vx2 = ux2 + 2gs

g = 0

∴ vx2 = ux2 + 0

vx2 = ux2

∴ vx = ux

Question 2

A body is projected at an angle of 30oto the horizontal with a velocity of 150 ms-1. Calculate the time it takes the greatest height. [Take g = 10 ms-2 and neglect air resistance]

Answer

Given:

  • θ = 30o
  • u = 150 ms-1
  • t = ?
  • g = 10 ms-2
  • The time taken to reach maximum height, t =?

Recall that

t = \( \frac{usin \theta}{g}\)

t = \( \frac{150 \: \times \: sin 30^o}{10}\)

t = \( \frac{75}{10}\)

= 7.5 s

Question 3

A wire of length 2.00 m and radius 1.0 mm is stretched by 25.0 mm on the application of a force of 103 N. Calculate the Young’s modulus for the wire.

Solution

Given:

  • L = 2 m
  • r = 1 mm = 1 × 10-3 m
  • e = 25 mm = 25 × 10-3 m
  • F = 1000 N

Young modulus, E = \( \frac{Fl}{Ae} \)

The area of a wire is the area of its cross-section, which is calculated using the formula A = πr2. In this formula, A is the area and r is the radius of the wire

Area, A = πr2 = 3.142 × (10-3)2 = 3.142 × 10-6

Young modulus, E = \( \frac{Fl}{Ae} \)

= \( \frac{1000 \: \times \: 2.00}{3.142 \: \times \: 10^{-6} \: \times \: 25 \: \times \: 10^{-3}} \)

= \( \scriptsize 2.547 \: \times \: 10^{10} \: NM^{-2} \)

Question 4

State three ways of increasing the rate of cooling of a cup of hot tea.

Answer

– Increasing the surface area by blowing

– Mixing

– Stirring

– Reducing the ambient temperature

Question 5

(a) What is doping in a semi-conductor?

Answer

Doping in a semiconductor is the addition of impurities to a pure semiconductor to increase its electrical conductivity through an increase in the number of holes and electrons or charge carriers.

 

(b) Draw the symbol for OR gate.

Answer

Question 6

 

(a) The circuit above consists of an a.c voltage input, a diode, a resistor, and a voltmeter. Identify the circuit.

Answer

The circuit is a half-wave rectifier

A half-wave rectifier converts an AC signal to DC by passing either the negative or positive half-cycle of the waveform and blocking the other. Half-wave rectifiers can be easily constructed using only one diode, but are less efficient than full-wave rectifiers.

 

(b) Draw the waveform for the output voltage.

Answer

Question 7

(a) Write the De Broglie equation.

Answer

De Broglie’s equation is given as:

⇒ \( \scriptsize \lambda = \normalsize \frac{h}{p} \\ \scriptsize = \normalsize\frac{h}{mv} \)

h = Planck’s constant

* It should be noted:

  • h = 6.63× 1034Js
  • mass of the wave-particle = m (in kg)
  • velocity of wave-particle = v (in ms-1)
  • momentum of wave-particle = p (in kg ms-1)

 

(b) Explain the significance of the equation

Answer

The significance of the equation is that it shows that matter has a dual nature, it can exist as a wave and as a particle.

De Broglie’s equation helps us understand the idea of matter having a wavelength \( \scriptsize \lambda = \normalsize \frac{h}{mv} \)

Therefore, if we look at every moving particle, whether microscopic or macroscopic, it will have a wavelength.

Question 8

(a) (i) Define uniform acceleration

Answer

Uniform acceleration is the acceleration of a body when it is undergoing a constant time rate of change in velocity.

(ii) Write an equation that relates linear velocity, angular velocity and radius of path in circular motion.

Answer

V = ωr

  • V = Linear/Tangential velocity
  • ω = Angular velocity
  • r = Radius

Linear velocity = Angular velocity × radius of path

 

(b) Two forces 30 N and 40 N act at right angles to each other. Determine by scale drawing, the magnitude and direction of the resultant force, using a scale of 1 cm of 5 N.

Answer

 

R2 = 302 + 402

R2 = 900 + 1600

R2 = 2500

R = \( \scriptsize \sqrt{2500} \)

R = 50 N

tan θ = \( \frac{opp}{adj}\\ = \frac{30}{40} \\ \scriptsize = 0.75 \)

θ = \( \scriptsize ta^{-1} \: 0.75 \\ \scriptsize = 36.9^o\)

 

(c) Explain why ships are usually refilled with sand and water after they have been emptied of their cargo.

Answer

A floating ship is balanced by its weight and upthrust on it. Hence when offloaded, the upthrust becomes greater than the weight of the ship, therefore, when refilled with sand and water, equilibrium is restored for stability.

 

(d) A crate of drinks of mass 20 kg is placed on a plane inclined at 30° to the horizontal. If the crate slides down with a constant speed,

(i) calculate the coefficient of kinetic friction

Answer

⇒ \( \scriptsize \mu = tan \theta \)

⇒ \( \scriptsize \mu = tan 30 \)

⇒ \( \scriptsize \mu = 0.5774 \)

or mg sin θ = μR

R = mg cos θ

R = 20 × 10 × cos θ = 173.2 N

μ = \( \frac{20 \: \times \: 10 \: \times \: \:sin \:30}{173.2}\\ = \scriptsize 0.58 \)

 

(ii) calculate the magnitude of the frictional force acting on the crate.

[g = 10 ms-2]

Solution

Frictional force, f = μR

R = mg cos θ

R = W cos θ

R = 200 cos θ

f = μ × 200 cos θ

f = 0.58 × 200 × 0.866

f = 100.46 N

Question 9

(a) Define specific latent heat of vaporization.

Answer

The specific latent heat of vaporization is the quantity of heat that is required to change the state of a unit mass of a liquid to a gaseous state.

 

(b) (i) What are renewable energy sources?

Answer

Renewable energy sources are the sources where replaceable energy being used up can be obtained or found. They are sources of energy that cannot be exhausted.

(ii) List four renewable energy sources.

Answer

The four sources include: – Sun – Wind – Water – Garbage (Biomass) – Geothermal, etc.

 

(c) Explain why tomatoes keep longer when kept in a moist jute bag in a clay pot.

Answer

A moist jute bag in a clay pot is always wet and the temperature is low and cool. The tomatoes kept in this bag are being preserved and with the low temperature, heat loss or gain will be neglected.

 

(d) (i) A box has a volume of 0.28 m3 and is 70% filled with iron fillings at 25°C. Calculate the total mass of the iron fillings

[Density of iron = 8.00 × 103 Kgm-3, specific latent heat of fusion of iron = 1.38 ×105 JKg-1, specific heat capacity of iron = 460 JKg-1K-1, melting point of iron = 1500°C]

Solution

Given:

Volume V = 0.28m3

The iron fillings volume = \( \frac{70}{100}\scriptsize \: \times \: 0.28 = 0.196 \: cm^3 \)

Total mass, m = ?

Density = \( \frac{mass}{volume} \)

Mass = Density × Volume

Mass = 8000 × 0.196 = 1568 kg

 

(ii) Calculate the energy required to melt 10% of the iron fillings.

Solution

Total mass of iron fillings = 1568 kg

mass of 10% of iron fillings = \( \frac{10}{100}  \: \times \: 1568 \\ = \scriptsize 156.8 \: kg \)

Energy = ml + mcΔθ

= ml + mc(θ2 – θ1)
= (156.8 × 1.38 × 105) + (156.8 × 460[1500 – 25])
= 0.216 × 108 + 1.06 × 108
= 1.28 × 108 J

Question 10

(a) (i) What is resonance?

Answer

Resonance is the effect felt/observed when a body vibrating with its own natural frequency transfers its frequency to the bodies around it, such that they all vibrate with the same frequency.

(ii) State two examples of resonance.

Answer

  • Vibrating tuning fork
  • Soldiers marching on a bridge
  • Repeated jumping of a diver at the free end of a diving board causes the board to resonate
  • Rattling of car engine at high speed causes the vibrating of the body of the car

 

(iii) Differentiate between loudness and intensity of sound

Answer

Intensity can be described as the rate of flow of energy per unit time; while loudness is the magnitude of the sensation resulting from a sound reaching the ear.

Loudness depends on the individual hearing ability while intensity depends on physical quantities of energy, time and area.

 

(b) When a ray is refracted through a rectangular glass prism, which of the following properties of the ray will change?
Wavelength, frequency, and speed.

Answer

Wavelength and speed will change and the frequency will remain constant.

 

(c)

(i) Copy the diagram above in your answer booklet.

(ii) On the copied diagram, sketch the pattern of the waves immediately after passing through the opening.

Answer

 

 

(d) (i) A diverging lens of focal length 18.0 m is used to view a shark that is 90.0 m away from the lens. If the image formed is 1.0 m long, calculate the image distance

Answer

Given:

  • Focal length, f = 18 m
  • Objective size, u = 90 m
  • Image size, v =  unknown
  • Image height, h = 1 m

⇒ \( \frac{1}{u} \: + \: \frac{1}{v}  = \frac{1}{f}  \)

⇒ \( \frac{1}{v} = \frac{1}{f} \: – \: \frac{1}{v}   \)

⇒ \( \frac{1}{v} = \frac{1}{-18} \: – \: \frac{1}{90}   \)

⇒ \( \frac{1}{v} = \frac{-5 – 1}{90}   \)

⇒ \( \frac{1}{v} = \frac{-6}{90}   \)

⇒ \( \frac{1}{v} = \frac{-1}{15}   \)

v = -15 m

The negative value of v indicates that v is a virtual image.

 

(ii) If the image formed is 1.0 m long, calculate the length of the shark.

Answer

M = \( \frac{v}{u} = \frac{Image \:height}{Object \:height}  = \frac{h_i}{h_o}\)

⇒ \( \scriptsize h_o = \normalsize \frac{h_i \: \times \: u }{v} \)

⇒ \( \scriptsize h_o = \normalsize \frac{1 \: \times \:90 }{15} \)

= 6.0 m

Question 11

(a) (i) Define the coulomb.

Answer

Coulomb is the quantity of electricity passing a section of a conductor in one second when the current is one ampere.

(ii) Define resistance

Answer

Resistance is the driving force that creates opposition to the flow of current in a circuit

 

(b) State the three effects of an electric current

Answer

– Chemical effect
– Magnetic effect
– Heating or thermal effect
– Optical effect

 

(c) (i) State the standard international colour convention for the insulating material covering this electrical wire in a three-pin plug.

(i) live; (ii) neutral; (iii) earth.

Answer

(i) Live – Red/Brown

(ii) Neutral – Blue/Black

(iii) Earth – Yellow/Green

 

(d) (i)

A watermelon of mass 5.0 kg is suspended on a uniform rod of mass 4.0 kg and 4.0 m long as illustrated in the diagram above. If the rod is in equilibrium by the action of the force between the charges +q and -q, calculate the anticlockwise moment

[g = 10 ms-2]

Solution

Anti-clockwise moment;

5gl1 = 5 × 10 × 1 = 50 Nm

 

(ii) calculate the value of q

Solution

sum of anti-clockwise moment = sum of clockwise moment

Find the sum of the clockwise moment, Cw

Cw = [4 × 10 × 1] + [F  × (2 + 1)]

Cw = [4 × 10 × 1] + [F × 3]

sum of clockwise moment, Cw = 40 + 3F

sum of anti-clockwise moment = sum of clockwise moment

∴ 50 = 40 + 3F

3F = 50 – 40

F = \( \frac{10}{3}\\ \scriptsize =  3.3\: N\)

To find q, use the formula below:

F = \( \frac{1}{4 \pi \varepsilon_0} \frac{q_1 q_2}{r^2}\)

or

F = \( \frac{kq_1 q_2}{r^2}\)

where k = \( \frac{1}{4 \pi \varepsilon_0} \scriptsize = 9 \: \times \: 10^9\: Nm^2C^{-2} \)

q1 = q2 = q

∴ F = \( \frac{k\: \times \: q \: \times \: q}{r^2}\)

F = \( \frac{k\: \times \: q ^2}{r^2}\)

q2 = \( \frac{Fr^2}{k} \)

q2 = \( \frac{3.3 \: \times \: 2.5^2}{9 \: \times \: 10^9} \)

q2 = \( \frac{3.3 \: \times \: 2.5^2}{9 \: \times \: 10^9} \)

q2 = \( \frac{20.625}{9 \: \times \: 10^9} \)

q2 = \( \scriptsize 2.29 \: \times \: 10^{-9} \)

q = \( \scriptsize \sqrt{2.29 \: \times \: 10^{-9}} \)

q = \( \scriptsize 4.79 \:  \times \: 10^{-5} \)

Question 12

(a) Define nucleon number

Answer

Nucleon number is the total number of proton of protons and neutrons in an atom of an element.

 

(b) (i) radioactive isotope of Americium (Am – 241) decays into nucleus of Neptunium (Np – 237) and an alpha (α) particle as shown in the nuclear equation below.

⇒ \( \scriptsize ^{241}_{95}Am\: \to \: ^{237}_{c}Np \: + \: ^b_a \alpha\)

State the number of neutrons in the nucleus of Americium 241.

Answer

⇒ \( \scriptsize ^{241}_{95}Am\)

  • nucleon number = 241
  • proton number = 95

Number of neutrons = nucleon number – proton number

Number of neutrons = 241 – 95 = 146

 

(b) Determine the values of a, b and c.

Answer

⇒ \( \scriptsize ^{241}_{95}Am\: \to \: ^{237}_{c}Np \: + \: ^b_a \alpha\)

Recall that \( \scriptsize ^{b}_{a}\alpha =\; ^{4}_{2}He \)

⇒ \( \scriptsize ^{241}_{95}Am\: \to \: ^{237}_{c}Np \: + \: ^{4}_{2}He\)

a = 2

b = 4

95 = c + 2;

c = 93

 

(c) (i) Why are γ-rays not deflected by electromagnetic fields?

Answer

γ-rays have no mass and no charge. Electromagnetic field has no effect on them.

(ii) State two properties of gamma rays that make them suitable for sterilizing medical equipment.

Answer

– High penetrating energy that makes it pass through tissues and kill viruses and bacteria
– Ionization energy: They are ionizing radiations.

 

(d) A sample of radioactive substance was found to be left with 1/32 of its initial count rate after 110 years. Calculate its decay constant.

Solution

Remaining = \( \frac{1}{2} \)

After first half-life = \( \frac{N}{2} \)

Second = \( \frac{N}{2} \: \times \: \frac{1}{2} = \frac{N}{4} \)

Third = \( \frac{N}{4} \: \times \: \frac{1}{2} = \frac{N}{8} \)

Fourth = \( \frac{N}{8} \: \times \: \frac{1}{2} = \frac{N}{16} \)

Fifth = \( \frac{N}{16} \: \times \: \frac{1}{2} = \frac{N}{32} \)

⇒ \( \frac{110}{5} \scriptsize = 22\: years\)

Decay constant, λ = \( \frac{0.693}{t_{\frac{1}{2}}} \\ = \frac{0.693}{22}\\\scriptsize = 0.315 \: s^{-1}\)

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