The speed of a falling object is directly proportional to the time for which it falls. The speed after 5 seconds is 49 metres/seconds. What is the speed of an object which falls for 8 seconds?
solving as a proportion:
v = kt
for the given:
49 = k*5
k = 9.8
so v = 9.8t
when t = 8
v = 9.8*8 = 78.4
or , as a simple ratio
v1/v2 = t1/2
49/t2 = 5/8
5t2 = 49*8
t2 = 49*8/5 = 78.4