# The subway escalator moves at a speed of 0.8 m / s. Find the time it takes a passenger to move 40m

**The subway escalator moves at a speed of 0.8 m / s. Find the time it takes a passenger to move 40m if he himself walks in the direction of travel at a speed of 0.2 m / s**

Ve = 0.8 m / s.

Vp = 0.2 m / s.

S = 40 m.

t -?

To find the time of movement of the passenger t, it is necessary to divide his path S by the speed of movement V: t = S / V.

According to the law of relativity of motion, the passenger’s speed relative to the stationary frame of reference V (relative to the ground) is equal to the sum of the speed of the moving frame of reference relative to the stationary Ve (the speed of the escalator relative to the ground) and the speed of the body relative to the moving frame of reference Vp (the speed of the passenger relative to the escalator): V = Ve + Vp.

t = S / (Ve + Vp).

t = 40 m / (0.8 m / s + 0.2 m / s) = 40 s.

Answer: the passenger will move along the escalator in time t = 40 s.