Question

A radar sends a signal to an aeroplane at a distance of 45 km away with a speed of 3 × 10⁸ m s⁻¹. After how long is the signal received back from the aeroplane?

Answer 1

Given Data:

Distance (d) = 45 km = 45 × 1000 m = 45,000 m

Speed of signal (v) = 3 × 10⁸ m s⁻¹

Formula:

Since the radar signal travels to the aeroplane and bounces back (echo principle), it | covers twice the distance (2d).

2d = v × t

t = `(2d)/v`

= `(2 xx 45000)/(3 xx 10^8)`

= `90000/(3 xx 10^8)`

= `(9 xx 10^4)/(3 xx 10^8)`

= 3 × 10⁻⁴ s

= 0.0003 s