SET 02
🎯 Objectives: TOWARD NECTA Physics - Set 2 Questions and Answers
NECTA Form Four Physics - Set 2
Competence-Based Conceptual Questions and Answers with Examples (35 Total)
1. Why does a ball thrown upwards slow down and fall back?
Gravity acts downward, opposing the motion upward, slowing the ball until velocity becomes zero, then pulls it back down.
Example: A football kicked straight up comes back due to Earth’s gravity.
2. Why is water used in car radiators?
Water has a high specific heat capacity, so it absorbs large amounts of heat without a large rise in temperature.
Example: In long trips, radiators prevent engine overheating by circulating water.
3. Why does a glass crack when hot water is poured in suddenly?
The inner surface expands quickly while the outer stays cool, causing uneven stress leading to cracking.
Example: Pouring boiling tea into a cold glass can shatter it.
4. Why do your ears pop in an airplane?
Changes in air pressure cause the eardrum to adjust; the popping is the ear balancing internal pressure with the external.
Example: When ascending or descending in a flight, ears may pop to equalize pressure.
5. Why do shadows form?
Shadows form when an opaque object blocks light rays from reaching a surface.
Example: Standing in sunlight creates a shadow on the ground behind you.
6. Why do metals expand when heated?
Heat increases the kinetic energy of particles, causing them to vibrate and move farther apart.
Example: Railway tracks have expansion gaps to prevent buckling in hot weather.
7. Why does water cool faster in a windy place?
Wind increases evaporation rate by removing warm water vapor from the surface.
Example: Wet clothes dry faster on a windy day than in still air.
8. Why is it hard to open a tightly closed jar lid?
Vacuum or pressure difference inside the jar resists external force, requiring more torque to open.
Example: Using a rubber grip helps open a tight jar by increasing friction.
9. Why is an earth wire used in appliances?
It provides a low-resistance path for current to prevent electric shock in case of insulation failure.
Example: A metal toaster has an earth wire to carry leakage current safely to the ground.
10. Why do we feel cold when sweat evaporates?
Evaporation absorbs heat from the skin, reducing body temperature.
Example: Sweating during exercise cools the body naturally.
11. Why does a boat float on water?
The boat displaces enough water such that the upward buoyant force equals its weight.
Example: A steel ship floats because its shape allows displacement of a large volume of water.
12. Why are transformers not used with DC current?
Transformers require a changing magnetic field to work, which only AC provides.
Example: Transformers step down 240V AC to 12V AC for chargers, not usable with DC.
13. Why do we hear echoes in empty rooms?
Sound reflects off hard surfaces and returns to the listener after a short delay.
Example: In a large empty hall, claps produce a distinct echo sound.
14. Why is lightning seen before thunder is heard?
Light travels faster than sound, so we see lightning before hearing the thunder it produces.
Example: During storms, there’s always a gap between the flash and the thunder sound.
15. Why does a charged balloon stick to a wall?
It induces opposite charges on the wall surface, causing attraction due to electrostatic forces.
Example: Rubbing a balloon on hair and placing it on a wall makes it cling.
16. Why does ice melt faster in metal than in plastic containers?
Metals are better conductors of heat, transferring thermal energy to the ice faster than plastic.
Example: Ice cubes placed in a steel bowl melt faster than those in a plastic bowl.
17. Why do mirrors reverse images left-to-right?
Mirrors reflect light perpendicularly; the reversal is due to our brain interpreting the direction change.
Example: Text appears reversed in a mirror because left and right orientations swap visually.
18. Why are bicycle tires pumped hard?
To increase air pressure inside, providing better support and reducing surface contact resistance.
Example: Under-inflated tires feel heavy and wear out quickly.
19. Why does a pencil look bent in a glass of water?
Due to refraction, light changes speed and direction when passing from water to air.
Example: A spoon in a glass appears broken at the water surface.
20. Why does a burnt filament bulb not light?
The filament breaks, interrupting the circuit so current cannot pass through to produce light.
Example: A bulb that clicks but doesn’t light usually has a broken filament.
21. Why does oil float on water?
Oil is less dense than water and is immiscible, so it floats as a separate layer.
Example: In cooking, oil always forms a layer above water in a pot.
22. Why do we use rubber handles in saucepans?
Rubber is a poor conductor of heat, preventing burns when touching hot cookware.
Example: Most cookware has insulated rubber or plastic handles.
23. Why does a parachute slow a falling person?
It increases air resistance, reducing acceleration and slowing down the fall.
Example: Skydivers open parachutes to reduce speed before landing.
24. Why does a magnet attract iron but not plastic?
Iron is a magnetic material; plastic is not affected by magnetic fields.
Example: A magnet on a fridge sticks to steel doors but not plastic handles.
25. Why is pressure less on snowshoes?
The large surface area distributes weight over a bigger area, reducing pressure on snow.
Example: Snowshoes prevent sinking in snow by spreading body weight.
26. Why is the vacuum inside a thermos flask important?
It prevents heat transfer by conduction and convection, maintaining temperature.
Example: Hot tea in a thermos stays warm for hours due to the vacuum insulation.
27. Why does touching metal in winter feel colder?
Metal conducts heat away from your skin faster than air or wood.
Example: Grabbing a metal pole on a cold day feels freezing compared to a plastic one.
28. Why do you lean forward when climbing a hill?
To shift your center of gravity over your feet and maintain balance.
Example: Hikers bend forward when climbing steep slopes to avoid falling backward.
29. Why does pressure cooker cook food faster?
It increases pressure, raising the boiling point of water so food cooks at a higher temperature.
Example: Meat cooks quickly in a pressure cooker due to steam pressure build-up.
30. Why does increasing temperature increase resistance in metal wires?
Higher temperatures cause atoms to vibrate more, making it harder for electrons to flow.
Example: Tungsten filament in a bulb gets hot and increases resistance as it glows.
31. Why is refraction important in lens design?
Refraction allows bending of light rays to focus them, forming images.
Example: Eyeglasses correct vision using lenses that refract light to the retina properly.
32. Why do satellites stay in orbit?
They have enough horizontal velocity to keep falling around Earth instead of crashing into it.
Example: Communication satellites orbit Earth continuously due to balance between gravity and speed.
33. Why does a wire heat up when current flows?
Electric current encounters resistance in the wire, converting electrical energy into heat.
Example: Electric kettles heat water using a coiled resistance wire.
34. Why do birds perch on high-voltage wires safely?
No potential difference across their feet, so no current flows through them.
Example: A bird touching only one wire isn’t shocked, but touching two wires could be fatal.
35. Why are turbines used in hydroelectric power plants?
They convert the kinetic energy of falling water into mechanical energy, which is then converted to electricity by generators.
Example: At Mtera Dam in Tanzania, falling water spins turbines to produce electrical power.
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