While looking out the window, you see lightning flash and then two seconds later, you hear the thunder. How far was the lightening from you

s = 686 m

Explanation:

Let,

time taken by light to reach the window = t

therefore,

time taken by sound to reach window = t + 2

speed of light = c = 3 x 10⁸ m/s

speed of sound = v = 343 m/s

Now, the distance covered by both light and sound is same. Therefore,

(s) light = (s) sound

(c) (t) = (v) (t + 2)

(3 x 10⁸) t = (343) (t + 2)

(3 x 10⁸ - 343) t = 686

t = 686/2.99 x 10⁸

t = 2.3 x 10⁻⁶ s

Now, the distance of lightning from window will be:

s = ct

s = (3 x 10⁸ m/s) (2.3 x 10⁻⁶ s)

s = 686 m