Two ships, A and B st out from port O simultaneously. A travels due north at 16 km/h, B due east at 13 km/h. The ships radio have a rang of 120. For how long would they remain in contact if B had travelled north-east

1 answer

Range,r = 120 km
and since the two ships are travelling at 90° to each other, we use Pythagoras:
distance, d = sqrt(Va^2+Vb^2)*t
t=time in hours
Va = speed of ship A
Vb = speed of ship B
In other words, the ships are in range as long as
d<r,
t√(Va²+Vb²)< 120
t<120/(√(Va²+Vb²))