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SS3 Physics Past Questions And Answers

Here are some SS3 Physics past questions and answers (2024 standard) covering different topics:


1. MECHANICS

Question 1: A force of 10 N is applied to a body of mass 2 kg. Calculate its acceleration.
Answer:
Using Newton’s second law:


F = ma

10 = 2a ]


a = \frac{10}{2} = 5 \text{ m/s}^2

Question 2: A ball is thrown vertically upwards with a speed of 20 m/s. How long will it take to reach its highest point? (Take m/s²).
Answer:
At the highest point, final velocity , initial velocity m/s. Using:


v = u - gt

0 = 20 – 10t ]


t = \frac{20}{10} = 2 \text{ s}

2. WAVES & OPTICS

Question 3: The speed of sound in air is 340 m/s. If a sound wave has a frequency of 1700 Hz, what is its wavelength?
Answer:
Using:


v = f\lambda

\lambda = \frac{v}{f} = \frac{340}{1700} = 0.2 \text{ m} ]

Question 4: A concave mirror has a focal length of 10 cm. If an object is placed 30 cm in front of the mirror, find the image distance.
Answer:
Using mirror formula:


\frac{1}{f} = \frac{1}{u} + \frac{1}{v}

\frac{1}{10} = \frac{1}{30} + \frac{1}{v} ]


\frac{1}{v} = \frac{1}{10} - \frac{1}{30} = \frac{3}{30} - \frac{1}{30} = \frac{2}{30} = \frac{1}{15}

v = 15 \text{ cm} ]


3. ELECTRICITY & MAGNETISM

Question 5: A 12 V battery is connected across a 6 Ω resistor. Find the current flowing through the circuit.
Answer:
Using Ohm’s Law:


V = IR

I = \frac{V}{R} = \frac{12}{6} = 2 \text{ A} ]

Question 6: If a transformer has 200 turns in the primary coil and 50 turns in the secondary coil, what is the transformation ratio?
Answer:


\text{Transformation ratio} = \frac{N_s}{N_p} = \frac{50}{200} = 0.25

4. HEAT ENERGY

Question 7: The specific heat capacity of water is 4200 J/kg°C. How much heat is required to raise the temperature of 2 kg of water from 20°C to 80°C?
Answer:
Using:


Q = mc\Delta T

Q = 2 \times 4200 \times (80 – 20) ]


Q = 2 \times 4200 \times 60

Q = 504000 \text{ J} ]

Question 8: Define latent heat of fusion.
Answer: Latent heat of fusion is the amount of heat required to convert a unit mass of a solid into a liquid without a change in temperature.


5. MODERN PHYSICS

Question 9: If the work function of a metal is 2 eV and a photon of energy 5 eV strikes the surface, what is the kinetic energy of the emitted electron?
Answer:
Using Einstein’s photoelectric equation:


KE = hf - \phi

KE = 5 – 2 = 3 \text{ eV} ]

Question 10: What is the half-life of a radioactive substance if its activity reduces to ¼ of its original value in 8 hours?
Answer:
Since the activity reduces to ¼, it means two half-lives have passed:


2T_{1/2} = 8

T_{1/2} = \frac{8}{2} = 4 \text{ hours} ]


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