Hey there! If you’re preparing for the JKSSB Forester exam or a similar competitive test, you know that the ‘Basic Science’ section can feel a bit daunting. I remember when I was studying for my own competitive exams, physics was the subject I’d sometimes try to skip over. But trust me, getting a solid grip on these fundamental concepts is not just about passing a test—it’s about building a foundation of knowledge that makes sense of the world around us, whether you’re in a forest or a lab.
Based on my experience tutoring students for these exams, I’ve put together a focused set of 25 multiple-choice questions. These aren’t just random questions; they cover the exact type of core physics principles that exam boards love to test. Let’s dive in and clarify these concepts together.
Basic Science (Physics) – Essential Practice Questions
Here are 25 key questions. I recommend trying to answer each one on your own before checking the explanation. That active recall is what truly builds understanding and helps the information stick for exam day.
Q1. Which of the following is a scalar quantity?
- (a) Velocity
- (b) Acceleration
- (c) Force
- (d) Mass
Answer: (d) Mass
Explanation: This is a crucial distinction. Scalar quantities have only magnitude (size or amount), while vectors have both magnitude and direction. Think of mass like this: if you have a 5 kg bag of rice, that’s just a description of how much stuff is there—no direction is involved. Velocity, acceleration, and force all require you to specify a direction to be complete.
Q2. The S.I. unit of power is:
- (a) Joule
- (b) Watt
- (c) Newton
- (d) Pascal
Answer: (b) Watt
Explanation: Power is all about rate. It’s how quickly work is done or energy is used. The Joule is the unit of energy or work. The Watt is defined as one Joule per second (1 W = 1 J/s). It’s named after James Watt, the steam engine pioneer. When you check a light bulb, you’re seeing its power rating in Watts.
Q3. What causes a body to continue in its state of rest or of uniform motion in a straight line, unless acted upon by an external force?
- (a) Momentum
- (b) Impulse
- (c) Inertia
- (d) Gravity
Answer: (c) Inertia
Explanation: This is the classic statement of Newton’s First Law of Motion. Inertia is the natural tendency of an object to resist any change to its state of motion. You feel this when a car suddenly brakes and you lurch forward—your body wants to keep moving at the original speed.
Q4. A moving object has kinetic energy. What is the formula for kinetic energy?
- (a) $PE = mgh$
- (b) $KE = \frac{1}{2}mv^2$
- (c) $W = Fd$
- (d) $P = VI$
Answer: (b) $KE = \frac{1}{2}mv^2$
Explanation: Kinetic energy is the energy of motion. Notice how it depends on the square of the velocity. This means if you double an object’s speed, its kinetic energy increases by a factor of four. This formula is central to understanding everything from falling objects to vehicle collisions.
Q5. The phenomenon responsible for the twinkling of stars is:
- (a) Dispersion of light
- (b) Total internal reflection
- (c) Atmospheric refraction
- (d) Scattering of light
Answer: (c) Atmospheric refraction
Explanation: Stars don’t actually twinkle; it’s an effect of our atmosphere. The light from a distant star travels through many kilometers of air, which has layers of varying density and temperature. These layers constantly bend (refract) the starlight in small, shifting ways, making the star’s apparent position and brightness flicker. Planets usually don’t twinkle as much because they are closer and appear as tiny disks, not points of light.
Q6. Which color of light deviates the most when passing through a prism?
- (a) Red
- (b) Orange
- (c) Green
- (d) Violet
Answer: (d) Violet
Explanation: This is a key result of dispersion. In the visible spectrum, violet light has the shortest wavelength and the highest frequency. When entering a medium like glass, shorter wavelengths slow down and bend more than longer wavelengths. That’s why violet is always at the most bent end of a rainbow or spectrum, with red at the other.
Q7. What is the S.I. unit of electric current?
- (a) Volt
- (b) Ohm
- (c) Ampere
- (d) Watt
Answer: (c) Ampere
Explanation: It’s easy to mix these up, so here’s a simple way to remember: Current is the flow of charge, and its unit is the Ampere (A), named after André-Marie Ampère. Think of it as the “flow rate” of electricity in a wire. Volts measure the “push” (potential difference), Ohms measure the “resistance” to flow, and Watts measure the “rate of energy use” (power).
Q8. According to Ohm’s Law, if voltage (V) is applied across a resistor (R), the current (I) flowing through it is given by:
- (a) $I = VR$
- (b) $I = R/V$
- (c) $I = V/R$
- (d) $I = V+R$
Answer: (c) $I = V/R$
Explanation: Ohm’s Law ($V = IR$) is the cornerstone of basic circuit theory. The rearranged form, $I = V/R$, tells you that for a fixed resistance, more voltage means more current. For a fixed voltage, more resistance means less current. It’s a direct and inverse relationship that governs how simple electrical devices work.
Q9. The instrument used to measure electric potential difference is:
- (a) Ammeter
- (b) Voltmeter
- (c) Galvanometer
- (d) Ohmmeter
Answer: (b) Voltmeter
Explanation: The names are your best clue here. A voltmeter measures volts (potential difference). A key practical point: in a circuit, an ammeter is connected in series to measure the current flowing through a branch, while a voltmeter is connected in parallel across the component to measure the voltage drop across it.
Q10. Which type of mirror is used as a rearview mirror in vehicles?
- (a) Plane mirror
- (b) Concave mirror
- (c) Convex mirror
- (d) Cylindrical mirror
Answer: (c) Convex mirror
Explanation: This is a perfect example of physics applied for safety. A convex mirror (curved outward) always produces a virtual, erect, and diminished (smaller) image. The “diminished” part is key—it allows the mirror to show a much wider field of view than a plane mirror, helping drivers see more of the traffic behind them. The trade-off is that objects appear farther away than they actually are, which is why these mirrors carry the warning “Objects in mirror are closer than they appear.”
Q11. The S.I. unit of frequency is:
- (a) Meter
- (b) Second
- (c) Hertz
- (d) Radian
Answer: (c) Hertz
Explanation: Frequency is how often something happens per unit of time. One Hertz (Hz) means one cycle or oscillation per second. It’s named after Heinrich Hertz, who proved the existence of electromagnetic waves. Whether it’s the hum of an engine, a sound wave, or a radio signal, frequency in Hz tells you how fast it’s vibrating.
Q12. What is the fundamental reason for the occurrence of seasons on Earth?
- (a) Earth’s rotation on its axis
- (b) Earth’s elliptical orbit around the Sun
- (c) The tilt of Earth’s axis relative to its orbital plane
- (d) Changes in the Sun’s activity
Answer: (c) The tilt of Earth’s axis relative to its orbital plane
Explanation: This is a common misconception. Many people think seasons are caused by the Earth being closer or farther from the Sun in its elliptical orbit. While the distance varies slightly, the primary cause is the axial tilt of about 23.5 degrees. This tilt means that for half the year, the Northern Hemisphere is tilted toward the Sun (receiving more direct sunlight and experiencing summer), and for the other half, it’s tilted away (receiving less direct sunlight and experiencing winter).
Q13. Light travels fastest in which of the following media?
- (a) Water
- (b) Glass
- (c) Air
- (d) Vacuum
Answer: (d) Vacuum
Explanation: Light is an electromagnetic wave. Unlike sound, it does not need a medium to travel. In fact, it travels fastest when there’s nothing in its way. In a perfect vacuum, light speed is approximately 300,000 kilometers per second (3 x 10^8 m/s). When it enters any material like air, water, or glass, it slows down due to interactions with atoms, which is what causes refraction.
Q14. The phenomenon of splitting of white light into its constituent colors when passing through a medium like a prism is called:
- (a) Reflection
- (b) Refraction
- (c) Dispersion
- (d) Diffraction
Answer: (c) Dispersion
Explanation: While refraction (bending) is involved, the specific name for the splitting into a spectrum is dispersion. It happens because the index of refraction of a material like glass is slightly different for each color (wavelength). Shorter wavelengths (violet/blue) bend more than longer ones (red). A rainbow is nature’s most beautiful display of dispersion in water droplets.
Q15. Why does the sky appear blue?
- (a) Due to reflection of blue light from oceans
- (b) Due to scattering of blue light by atmospheric particles
- (c) Due to absorption of other colors of light
- (d) Due to the presence of blue colored gases in the atmosphere
Answer: (b) Due to scattering of blue light by atmospheric particles
Explanation: This is called Rayleigh scattering. The molecules and tiny particles in our atmosphere are much better at scattering short-wavelength light (blue and violet) than longer wavelengths (red and yellow). So, when sunlight enters the atmosphere, the blue light is scattered in all directions, filling the sky with blue light. At sunrise and sunset, the light travels through more atmosphere, scattering away most of the blue and letting the longer red and orange wavelengths reach our eyes directly.
Q16. Which of the following is a non-renewable source of energy?
- (a) Solar energy
- (b) Wind energy
- (c) Coal
- (d) Hydropower
Answer: (c) Coal
Explanation: This distinction is vital for environmental science. Non-renewable resources like coal, oil, and natural gas are formed over millions of years from ancient organic matter. We are consuming them far faster than they can be replenished. Renewable sources like solar, wind, and hydropower are essentially inexhaustible on human timescales because they are constantly replenished by natural processes.
Q17. A device that converts electrical energy into mechanical energy is called a:
- (a) Generator
- (b) Transformer
- (c) Motor
- (d) Rectifier
Answer: (c) Motor
Explanation: Remember the pair: Motor and Generator. An electric motor uses electricity to create motion (think fan, drill, electric vehicle). A generator does the opposite—it uses mechanical motion (from steam, water, wind) to produce electricity. A transformer changes voltage levels, and a rectifier converts AC to DC.
Q18. The S.I. unit of heat is:
- (a) Calorie
- (b) Joule
- (c) Degree Celsius
- (d) Kelvin
Answer: (b) Joule
Explanation: Heat is a transfer of thermal energy. Since energy is the capacity to do work, and the S.I. unit of work and all forms of energy is the Joule, heat is also measured in Joules. The calorie is an older unit still used in nutrition (1 calorie = about 4.184 Joules). Degrees Celsius and Kelvin are units of temperature, which measures the average kinetic energy of particles, not the total heat content.
Q19. What is the principle behind the working of a hydraulic lift?
- (a) Bernoulli’s Principle
- (b) Archimedes’ Principle
- (c) Pascal’s Principle
- (d) Newton’s Law of Gravitation
Answer: (c) Pascal’s Principle
Explanation: Pascal’s Principle states that pressure applied to a confined fluid is transmitted equally and undiminished in all directions. In a hydraulic lift, a small force applied to a small-area piston creates a pressure. This same pressure acts on a much larger-area piston, resulting in a
