About this quiz
50 questions covering every section of the note on SI units, motion, gravity, work and energy, pressure, heat, light, sound and electricity.
This Lok Sewa practice set has 50 multiple-choice questions (Subject: Science and Technology · For: Kharidar, Nayab Subba, Section Officer · Level: Easy). Take the quiz above first; after that, use the study list below to revise every question with its correct answer and a short explanation.
Study list: all 50 questions with answers and explanations
What is the SI unit of mass?
- A) Gram
- B) Kilogram ✔
- C) Newton
- D) Pound
Why: Kilogram is one of the seven SI base units; newton is the unit of force, not mass.
Which of these is NOT one of the seven SI base units?
- A) Ampere
- B) Candela
- C) Mole
- D) Joule ✔
Why: Joule is a derived unit of energy; ampere, candela and mole are all base units.
Pascal is the SI unit of which quantity?
- A) Pressure ✔
- B) Power
- C) Frequency
- D) Charge
Why: Pressure = force ÷ area, and its SI unit is the pascal (1 newton per square metre).
The hertz (Hz) measures what?
- A) Resistance
- B) Energy
- C) Frequency ✔
- D) Force
Why: One hertz means one cycle or vibration per second.
Which of the following is a vector quantity?
- A) Velocity ✔
- B) Speed
- C) Mass
- D) Time
Why: Velocity has both size and direction, so it is a vector; speed has size only.
A bus moves at 72 km/h. What is its speed in m/s?
- A) 15 m/s
- B) 36 m/s
- C) 20 m/s ✔
- D) 25 m/s
Why: Multiply by 5/18: 72 × 5/18 = 20 m/s.
Standing passengers lean forward when a moving bus stops suddenly. Which law explains this?
- A) Newton's third law
- B) Newton's first law (inertia) ✔
- C) Ohm's law
- D) Law of reflection
Why: Their bodies tend to keep moving because of inertia, as stated in Newton's first law.
A force of 10 N acts on a trolley of mass 2 kg. What is its acceleration?
- A) 20 m/s²
- B) 12 m/s²
- C) 8 m/s²
- D) 5 m/s² ✔
Why: From F = m × a, a = F ÷ m = 10 ÷ 2 = 5 m/s².
The backward movement (recoil) of a gun when it is fired is an example of which law?
- A) Newton's first law
- B) Newton's third law ✔
- C) Law of conservation of mass
- D) Newton's second law
Why: The bullet is pushed forward and the gun is pushed back with an equal and opposite reaction.
What is the approximate value of g near the Earth's surface?
- A) 9.8 m/s² ✔
- B) 98 m/s²
- C) 1.6 m/s²
- D) 3 m/s²
Why: The acceleration due to gravity near the Earth's surface is about 9.8 m/s².
A person has a mass of 60 kg on Earth. What is the mass on the Moon?
- A) 10 kg
- B) 360 kg
- C) Zero
- D) 60 kg ✔
Why: Mass is the amount of matter and stays the same everywhere; only weight changes.
In which unit is weight measured?
- A) Kilogram
- B) Joule
- C) Newton ✔
- D) Watt
Why: Weight is a force (mass × g), so its SI unit is the newton.
A man pushes hard against a wall but the wall does not move. How much work does he do in physics?
- A) Zero ✔
- B) Equal to his weight
- C) Very large
- D) Equal to the force applied
Why: Work = force × distance moved; since the wall does not move, the work done is zero.
Water stored behind a dam mainly has which type of energy?
- A) Kinetic energy
- B) Potential energy ✔
- C) Sound energy
- D) Light energy
Why: The water has energy because of its height, which is potential energy (PE = mgh).
The idea that energy cannot be created or destroyed but only changed in form is called what?
- A) Newton's second law
- B) Ohm's law
- C) Law of conservation of energy ✔
- D) Law of inertia
Why: This is the law of conservation of energy, seen for example in a hydropower plant.
A machine does 600 J of work in 3 seconds. What is its power?
- A) 1800 W
- B) 603 W
- C) 300 W
- D) 200 W ✔
Why: Power = work ÷ time = 600 ÷ 3 = 200 W.
Why does a sharp knife cut better than a blunt one?
- A) It is heavier
- B) It has more mass
- C) It has less friction with air
- D) It puts the force on a smaller area, giving more pressure ✔
Why: Pressure = force ÷ area, so a thin edge produces greater pressure for the same force.
A 12 V battery is connected across a 4 Ω resistor. What current flows?
- A) 3 A ✔
- B) 48 A
- C) 16 A
- D) 8 A
Why: By Ohm's law, I = V ÷ R = 12 ÷ 4 = 3 A.
Normal human body temperature is 37 °C. What is it in Fahrenheit?
- A) 37 °F
- B) 310 °F
- C) 98.6 °F ✔
- D) 66.6 °F
Why: F = 9/5 × 37 + 32 = 66.6 + 32 = 98.6 °F.
Why does water boil below 100 °C in the high mountain areas of Nepal?
- A) The water there is purer
- B) The air pressure there is lower ✔
- C) The Sun is closer
- D) The air pressure there is higher
Why: Lower air pressure at height lowers the boiling point; a pressure cooker raises it again.
A person cannot see far objects clearly. Which defect is this and which lens corrects it?
- A) Hypermetropia, convex lens
- B) Myopia, convex lens
- C) Myopia, concave lens ✔
- D) Hypermetropia, concave lens
Why: In myopia the image forms in front of the retina, and a concave lens corrects it.
A rainbow is formed mainly because of which process?
- A) Dispersion of sunlight by raindrops ✔
- B) Reflection from clouds only
- C) Absorption of light by air
- D) Echo of light
Why: Raindrops split white sunlight into seven colours through refraction and reflection, which is dispersion.
Through which medium does sound travel fastest?
- A) Vacuum
- B) Air
- C) Water
- D) Steel ✔
Why: Sound travels fastest in solids such as steel and cannot travel through a vacuum at all.
A 100 W bulb is used for 10 hours. How much electrical energy does it use?
- A) 10 kWh
- B) 1 kWh ✔
- C) 0.1 kWh
- D) 1000 kWh
Why: 100 W × 10 h = 1000 Wh = 1 kWh, which is one unit on the bill.
What is the normal hearing range of the human ear?
- A) 2 Hz to 2,000 Hz
- B) 200 Hz to 200,000 Hz
- C) 20 Hz to 20,000 Hz ✔
- D) 20,000 Hz to 50,000 Hz
Why: Humans hear from 20 Hz to 20,000 Hz; sound above this is ultrasonic and below it is infrasonic.
The SI unit of length is the:
- A) Metre ✔
- B) Kilometre
- C) Foot
- D) Mile
Why: Metre.
The SI unit of time is the:
- A) Second ✔
- B) Minute
- C) Hour
- D) Day
Why: Second.
The SI unit of electric current is the:
- A) Ampere ✔
- B) Volt
- C) Ohm
- D) Watt
Why: Ampere.
The SI unit of temperature is the:
- A) Kelvin ✔
- B) Celsius
- C) Fahrenheit
- D) Joule
Why: Kelvin.
The SI unit of force is the:
- A) Newton ✔
- B) Joule
- C) Watt
- D) Pascal
Why: Newton.
The SI unit of energy/work is the:
- A) Joule ✔
- B) Watt
- C) Newton
- D) Volt
Why: Joule.
The SI unit of power is the:
- A) Watt ✔
- B) Joule
- C) Ampere
- D) Ohm
Why: Watt.
The SI unit of resistance is the:
- A) Ohm ✔
- B) Volt
- C) Ampere
- D) Tesla
Why: Ohm.
Speed is a scalar; velocity is a:
- A) Vector ✔
- B) Scalar
- C) Unit
- D) Constant
Why: Has direction.
Rate of change of velocity is called:
- A) Acceleration ✔
- B) Speed
- C) Momentum
- D) Force
Why: m/s².
Momentum equals:
- A) Mass × velocity ✔
- B) Mass × acceleration
- C) Force × time only
- D) Work ÷ time
Why: p = mv.
Newton's second law states:
- A) F = ma ✔
- B) Every action has an equal and opposite reaction
- C) A body stays at rest
- D) E = mc²
Why: Second law.
A rocket works on Newton's:
- A) Third law ✔
- B) First law
- C) Second law only
- D) Law of gravitation
Why: Action-reaction.
Kinetic energy is energy due to:
- A) Motion ✔
- B) Position
- C) Heat
- D) Light
Why: ½mv².
The speed of light in vacuum is about:
- A) 3 × 10^8 m/s ✔
- B) 3 × 10^5 m/s
- C) 340 m/s
- D) 1,500 m/s
Why: 300,000 km/s.
The speed of sound in air is about:
- A) 340 m/s ✔
- B) 3 × 10^8 m/s
- C) 1,500 m/s
- D) 30 m/s
Why: At room temperature.
Sound cannot travel through:
- A) Vacuum ✔
- B) Water
- C) Steel
- D) Air
Why: Needs a medium.
Sound above 20,000 Hz is called:
- A) Ultrasound ✔
- B) Infrasound
- C) Audible
- D) Noise
Why: Used in sonography.
Echo is caused by:
- A) Reflection of sound ✔
- B) Refraction
- C) Absorption
- D) Diffraction
Why: Reflected sound.
A convex lens is used to correct:
- A) Long-sightedness (hypermetropia) ✔
- B) Short-sightedness
- C) Colour blindness
- D) Astigmatism only
Why: Converging lens.
Bending of light when it passes from one medium to another is:
- A) Refraction ✔
- B) Reflection
- C) Dispersion
- D) Scattering
Why: Refraction.
The sky appears blue due to:
- A) Scattering of light ✔
- B) Reflection
- C) Refraction
- D) Absorption
Why: Rayleigh scattering.
Ohm's law states:
- A) V = IR ✔
- B) P = VI only
- C) F = ma
- D) E = mc²
Why: Voltage = current × resistance.
Electric power P equals:
- A) V × I ✔
- B) V ÷ I
- C) I ÷ R
- D) R × V
Why: Watts.
1 kWh (unit of electricity) equals:
- A) 1,000 watts used for 1 hour ✔
- B) 1 watt for 1 hour
- C) 100 watts for 1 hour
- D) 1 joule
Why: Commercial unit.