Elevator Problem

1. Jan 21, 2005

khf

A 56-kg girl weighs herself by standing on a scale in an elevator. What does the scale read when the elevator is ascending at 13m/s buts its speed is decreasing by 4m/s in each second?

I know you use Newton's second law, however, I do not know how to find acceleration..

2. Jan 21, 2005

Phymath

which direction is the acceration? If you figure that out you know which direction the force of the slowing elevator is. Add the wieght vector with the force vector to get her wieght...

the acceration if opposite the velocity ( girl weighs W = mg + ma_elevator)

3. Jan 21, 2005

Staff: Mentor

Apply the definition of acceleration: $a = \Delta v/\Delta t$. (Direction matters.)