science
posted by jo145578 .
a person walks up a stationary escalator in t1 second if he remains stationary on the escalator then it can take him up in t2 second if the length of the escalator is L,then
1.determine the speed of man with respect to escalator
2.determine the speed of escalator
3. how much time would it take him to walk up the moving escalator?

1) Speed of man w.r.t.escalator = L/t1
2) Speed of escalator w.r.t.ground = L/t2
3)Speed of man w.r.t.ground = (L/t1)+(L/t2)
Time taken by man to cover distance(L) = L/(L/t1)+(L/t2)
= t1*t2/(t1+t2) 
if a man moves up the escalator and the escalator moves down he has, for example, Vm/g=2stair/s and the escalator has Ve/g =1stair/s, so we have resultant velocity =3stairs/s. Now, assume that as the escalator is not moving man´s Vm/g moving up is 20stairs/s. So the man´s velocity is Vm/g / 3 =20/2> Vm/g =30stairs/s. Therefore his displacement is 30 stairs up