### Kinematics

is the length. is the time it takes to

walk on the stalled escalator. is the time it takes to

ride the moving escalator. is the time to walk up the moving

escalator.

The walking speed of the person relative to the stalled escalator

is .The speed of the escalator relative to

the ground is . The speed of the walking person

relative to the ground on a moving escalator is .

But these three speeds are related: .

Combine all this:

Put in the numbers and get .