Kinematics
What’s the unit of speed in SI?
meters per second(m/s)
What force always acts opposite to motion?
Friction
What type of energy is stored in a stretched rubber band?
Elastic potential energy
What is the SI unit of wavelength?
Meter (m)
Why do astronauts aboard the ISS feel weightless, even though gravity is still acting on them?
Because they are in free fall — the ISS and astronauts are constantly falling toward Earth, but moving forward fast enough to stay in orbit. They’re not without gravity; they’re in continuous free fall, so they feel weightless.
What’s the difference between speed and velocity?
Velocity includes direction; speed does not
A 5 kg object sits on a flat surface. What is the normal force acting on it? (Assume g = 9.8 m/s²)
49 N (Normal force = weight = mg = 5 × 9.8)
State the Law of Conservation of Energy.
Energy cannot be created or destroyed, only transformed or transferred.
A wave has a frequency of 5 Hz and wavelength of 3 m. What’s its speed?
15 m/s (v = fλ = 5 × 3)
We all know that light has no mass, yet gravity can bend its path — like how starlight curves around the Sun. But if gravity only pulls on mass, how can it affect something weightless like light?
Because gravity doesn’t just pull on mass — it bends space and time itself. Light always travels in the straightest possible path, called a “geodesic,” but when space is curved by a massive object (like the Sun), that path bends too. So light follows the curve of space — it’s not being pulled like a rock, it’s following the shape of spacetime.
If a car moves 60 km in 2 hours, what’s its average speed?
30 km/h
A 12 N force is applied to a 3 kg box. What is its acceleration? (Ignore friction)
4 m/s² (a = F/m = 12/3)
A 3 kg object is moving at 4 m/s. What is its kinetic energy?
24 J (KE = ½ × 3 × 4² = 24)
Define amplitude in terms of wave motion.
The maximum displacement of a point on the wave from its rest position.
Why does your coffee cool down over time, but it never spontaneously heats back up?
Because of the Second Law of Thermodynamics — energy naturally spreads out (entropy increases). Heat flows from hot to cold, not the other way around. Spontaneous heating would violate entropy, so it doesn't happen in nature.
Define acceleration
The rate of change of velocity
A 10 kg block is pulled with a force of 50 N. If there’s 20 N of friction opposing motion, what’s the acceleration?
3 m/s² (Net force = 30 N → a = 30/10)
A 5 kg rock is dropped from 10 m. What is its speed just before hitting the ground? (Assume no air resistance)
≈ 14 m/s (Use PE = KE → mgh = ½mv² → v = √(2gh) = √(2×9.8×10))
Why does sound travel faster in water than in air?
Because particles in water are more closely packed, allowing faster energy transfer.
You’re holding a magnet still next to a coil of wire. Nothing happens. But if you move the magnet, current flows. From the magnet’s perspective, it's not moving. Why does this still create electricity?
Because changing magnetic fields induce electric fields. This is Faraday’s Law, but special relativity adds depth: motion is relative, so either the magnet moves through the coil or the coil moves around the magnet — both create a changing field in one frame, causing electrons to move.
A train accelerates from rest at 2 m/s² for 10 seconds. What’s its final speed?
20 m/s (v = at = 2 × 10)
A 2-block system (4 kg and 2 kg) is pulled by a 36 N force on a frictionless surface. What is the tension between the two blocks?
12 N (Total a = F/(m1+m2) = 36/6 = 6 m/s² → Tension on 2 kg = 2×6 = 12 N)
A pendulum swings from a height of 2 m. At the lowest point, what type of energy does it have, and why is total energy conserved?
Kinetic energy; because potential energy is converted into kinetic energy without loss (ignoring friction).
A wave reflects off a surface. Describe what happens to its frequency, speed, and wavelength.
Frequency and speed stay the same; wavelength stays the same in the same medium. Direction reverses.
We all know that in quantum physics, tiny particles like electrons can behave like waves and exist in multiple states at once — a phenomenon called superposition. But if everything is made of atoms, why don’t we ever see big objects, like a baseball or a chair, doing the same strange quantum tricks?
Because quantum effects scale with Planck’s constant — they’re negligible for large masses. A baseball interacts with billions of particles and the environment, causing decoherence, which destroys superposition and entanglement. So classical behavior emerges naturally at macroscopic scales.