Medium
During a thunderstorm, the sound of thunder is heard 3 seconds after the lightning flash is seen. If the speed of sound in air is 340 m/s, how far away did the lightning strike? (Ignore the time taken by light.)
Explanation
Explanation
Step 1: Light travels at 3 × 10⁸ m/s, so we see the flash almost instantly. Sound is much slower, so thunder is heard later.
Step 2: Time delay between flash and thunder = 3 s, which is the time sound takes to travel the distance.
Step 3: Distance = speed × time = 340 × 3 = 1020 m.
Step 4: So the lightning struck about 1 km away.
Answer: 1020 m.
PRO TIP
Re-check your working by substituting the answer back into the original question.