Post-UTME Physics
Past Questions

AI Explanation

## The reasoning Force is what causes objects to accelerate — think of pushing a book or kicking a ball. In Physics, we define force using **Newton's Second Law**: F = ma (force equals mass times acceleration). The SI unit must match this definition: - Mass is measured in kilograms (kg) - Acceleration is measured in metres per second squared (m/s²) - So force = kg × m/s² = **Newton (N)** One Newton is the force needed to accelerate 1 kg of mass at 1 m/s². Simple! ## Why the wrong options tempt you **A) Joule** — This measures *energy* or *work* (force × distance). Easy to confuse because both involve force, but Joule measures the *result* of applying force over a distance. **C) Watt** — This measures *power* (energy per time). Students mix this up because force, energy, and power are related, but they're different quantities. **D) Pascal** — This measures *pressure* (force per area). Pressure uses force in its formula, but it's force *spread over* an area, not force itself. ## Quick takeaway **Force makes things move → Newton. Energy from movement → Joule. Pressure from spreading force → Pascal.** Each quantity has its own unit!

AI Explanation

**The reasoning** Speed tells us **how fast something moves**. To find speed, you need to know: - How far it traveled (distance) - How long it took to get there (time) The formula is: **Speed = Distance ÷ Time** Think about it: If you travel 100 km in 2 hours, your speed is 100 ÷ 2 = 50 km/h. You're dividing the distance covered by the time it took. This is a **fundamental definition** in Physics — speed is the rate of covering distance. **Why the wrong options tempt you** - **Force (A)** sounds physics-y, but force is about *push or pull* (F = ma), not how fast you move. - **Mass (C)** might confuse you because heavier objects *feel* slower, but mass doesn't define speed. - **Power (D)** relates to energy and work done per time, not distance covered per time. These options throw physics terms at you hoping you'll panic and guess. Don't fall for it! **Quick takeaway** Speed is always "distance per unit of time" — no distance, no time, no speed calculation!

AI Explanation

**The reasoning** An **echo** is that delayed sound you hear when you shout in an empty hall or near a mountain. It happens because sound waves bounce back to you from a hard surface — just like how light bounces off a mirror. This bouncing of waves off a surface is called **reflection**. The sound travels to the wall/cliff, hits it, and returns to your ears. If the reflecting surface is far enough (at least 17 meters away), you hear the original sound and the reflected sound as two separate events — that's your echo. **Why the wrong options tempt you** - **Refraction** (A) is bending of waves when moving between different media (like sound traveling from air into water) — no bouncing back involved. - **Diffraction** (C) is when waves spread around obstacles or through openings — think sound bending around a corner. - **Polarisation** (D) applies mainly to light waves oscillating in specific directions — not relevant to sound echoes. **Quick takeaway** Echo = sound **reflecting** back to you; if it bends or spreads, that's refraction or diffraction, not an echo.

AI Explanation

**The reasoning** Ohm's Law states that **voltage (V) is directly proportional to current (I) and resistance (R)**. Think of it like water flowing through a pipe: the voltage is the pressure pushing the water, current is how fast the water flows, and resistance is how narrow the pipe is. The formula is simply: **V = IR** So if a resistor has 5Ω resistance and 2A current flows through it: V = 2 × 5 = 10V This is one of the most fundamental laws in electricity — memorize it like your name! **Why the wrong options tempt you** - **A) I/R** — This actually gives you current when rearranged (I = V/R), but backwards here - **C) I²R** — This is the formula for *power dissipated as heat* (P = I²R), not voltage. Common mix-up! - **D) R/I** — Just scrambling the letters, hoping you're unsure **Quick takeaway** **"Voltage equals current times resistance: V = IR"** — say it until it's automatic. Everything else in circuits builds from this foundation!

AI Explanation

**The reasoning** This is about **metric prefixes** — the shortcuts we use to express large or small numbers in science. The prefix "kilo-" (symbol: k) always means "1000" in the metric system. Think of everyday examples: 1 kilogram = 1000 grams, 1 kilometer = 1000 meters, 1 kilowatt = 1000 watts. So: **1 kW = 1000 W** That's it! No calculation needed — just know what "kilo" means. --- **Why the wrong options tempt you** - **A) 10** — You might confuse "kilo" with "deci" (which means 1/10) - **B) 100** — This is "hecto" (symbol: h), like hectare. Easy mix-up if you're rushing - **D) 10,000** — This is actually "myria" (rarely used) or you're adding an extra zero by mistake The trap is forgetting which prefix means what power of 10. --- **Quick takeaway** **Kilo always equals 1000** — memorize this trio: kilogram (1000 g), kilometer (1000 m), kilowatt (1000 W). Once you lock in "kilo = 1000," you'll never miss these again!

AI Explanation

**The reasoning** Light travels in **straight lines** through a uniform medium — this is called **rectilinear propagation of light**. That's why: - Shadows have sharp edges (light can't bend around objects to fill them in) - You can't see around corners without a mirror - A laser pointer makes a perfectly straight beam - We use rulers to draw "lines of sight" in ray diagrams This straight-line motion continues until light hits a boundary (like glass or water), where it may reflect or refract, but even then, it travels in *new* straight lines, not curves. **Why the wrong options tempt you** - **A (Curves)**: You might think of light "bending" during refraction, but that's actually light changing direction *sharply* at the boundary between media, then continuing straight in the new direction. - **C (Circles) & D (Spirals)**: These sound scientific but have no basis. Light doesn't orbit or spiral naturally in normal conditions. **Quick takeaway** Light is the ultimate "straight shooter" — it only travels in straight lines unless something forces it to change direction, which is why shadows exist and you need mirrors to see around corners.

AI Explanation

**The reasoning** Energy of motion is called **kinetic energy (KE)**. This is the energy an object possesses simply because it's moving. Whether it's a ball rolling, a car driving, or even you running to catch a bus — that's all kinetic energy in action. The formula is: KE = ½mv², where m is mass and v is velocity. Notice how velocity appears in the formula? That's because the faster something moves, the more kinetic energy it has. A stationary object has zero KE because v = 0. **Why the wrong options tempt you** - **PE (Potential Energy)** is energy of *position*, not motion — like water stored high up in a tank - **Heat** is a *form* of energy transfer, not specifically energy of motion (though molecules do vibrate!) - **Sound** is also energy, but it's specifically energy traveling as vibrations through air or materials The trap is mixing up different energy types. They're all energy, but only KE directly describes motion. **Quick takeaway** Think: **K**inetic = **K**icking a ball — anything moving has KE!