Physics Is Closer Than You Think
Physics might conjure images of complex formulas, but we actually use physics laws every day. Calculating travel speed, understanding electricity bills, and adjusting cooking heat are all physics. Understanding a few key laws can answer many everyday questions.
Speed, Distance, and Time
Distance = Speed × Time
Speed = Distance ÷ Time
Time = Distance ÷ Speed
Real example: Seoul to Busan is about 400km. At 100 km/h average highway speed, it takes about 4 hours. The KTX train averaging 250 km/h takes about 1 hour 36 minutes.
Electricity Bills: Watts and Kilowatt-Hours
Energy (kWh) = Power (W) × Hours ÷ 1,000
Cost = Energy (kWh) × Rate (KRW/kWh)
| Appliance | Power | Daily Use | Monthly kWh | Monthly Cost |
|---|
| Air Conditioner | 1,500W | 8 hours | 360 kWh | ~50,000 KRW |
| Refrigerator | 100W | 24 hours | 72 kWh | ~10,000 KRW |
| Microwave | 1,000W | 20 min/day | 10 kWh | ~1,400 KRW |
| LED Light | 10W | 8 hours | 2.4 kWh | ~340 KRW |
| Washer | 500W | 1 hour/day | 15 kWh | ~2,100 KRW |
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Heat and Temperature: Physics in Cooking
Q = m × c × ΔT
= 1kg × 4,186 J/(kg·°C) × (100-20)°C = 334,880 J ≈ 80 kcal
Boiling 1L of water requires about 80 kcal of energy. A 2,000W electric kettle does this in about 2 minutes 47 seconds. A gas range (~3,000W) takes about 1 minute 52 seconds.
Car Fuel Efficiency Physics
Fuel Cost = (Distance ÷ Efficiency) × Fuel Price
Example: 400km ÷ 12km/L × 1,700 KRW/L = ~56,700 KRW
Eco-driving (avoiding sudden acceleration/braking, maintaining 80-100 km/h) can improve fuel efficiency by 10-15%.
Gravity and Falling Objects
- After 1 second: 9.8 m/s (~35 km/h), fallen 4.9m
- After 2 seconds: 19.6 m/s (~70 km/h), fallen 19.6m
- After 3 seconds: 29.4 m/s (~106 km/h), fallen 44.1m
This is why speeding is dangerous: doubling speed quadruples braking distance (kinetic energy = ½mv²).
Physics Makes Life Easier
- Save electricity: Reduce usage time of high-power appliances (AC, heaters).
- Save fuel: Maintain economic speed and avoid sudden acceleration.
- Cook efficiently: Covering pots reduces heat loss and speeds boiling by 30%.
- Drive safely: Reducing speed exponentially decreases braking distance.