Question

NCERT CLASS IX - Science Textbook
Chapter 8 - Motion

During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, that is, 3 × 108m s - '1.

Answer 1

Speed=Distance/time i.e s=d/t
=>d=sxt
Given,s=speed of light=3x10^8 m/s and t=5 minutes=5x60 secs.=300 s

So,d=3x10^8 x 300 mts.= 90 x 10^9 mts.

Answer 2

All electrical or electronic signals in air travel with the speed of light.  They are emitted by the space ship in space and are received by the Earth station.

Distance of space ship from the Earth station
                 = speed * time duration
                 = 3 * 10⁸  m/sec  * 5 * 60 seconds
                 = 9 * 10¹⁰  meters
                 =  9,00,00,000  km