more speed and distance

[fbray123]

if two objects are moving at different speeds and you know the speed of both and the time gap between them how could you work out the time it would take the faster moving rear object to catch the slower front object?

[tubeway]

Subtract the faster speed from the slower - and divide by the distance

Make sure you use the same type of measurement throughout of course i.e miles/kilometers seconds/hours

[Muppit]

He doesnt have the distance though... he only has the time gap.

Which is the answer?

Isn't it?

Crazy

My my, GCSE science homework has really gotten easy since I did it!

Mupp

[Trevilino]

But if he knows the time gap and the speed then the distance they were apart at that moment in time = t * f (T=time, f=speed of object behind) e.g. if they were 30 mins apart and the object behind was doing 30mph then it was 30*0.5 (15) miles behind at that time.
So just substitute t*f in Tubeway's equation i.e. Time to catch up would be (Speed a - Speed b)/(Speed a * time gap)

[Trevilino]

Having just looked at it again - it's the reciprocal of that equation i.e (Speed a * time gap)/(Speed a-Speed b)
Eg Car 1 doing 30mph is 1 hour adrift of Car 2 doing 15mph.
Time to catch up = (30*1)/(30-15) = 2 hours