Question

A 60 kg boy rides in an elevator that accelerates downward at 1.8 m/s. What is the net force excerted on the boy?

Answer 1

`"108 N"`

Explanation:

First thing's first: `"1.8 m/s"` is not an acceleration. It is a speed. We know that speed is how much position changes in time (so it has units of meters per second) and acceleration is change is velocity per time (so it has units of meters per second per second or meters per second squared). Units in physics are very important for understanding when things are right.

That being said, I'm going to assume that this is a typo (and you meant `"1.8 m/s"^2`, so that we can actually get a number out. We can use Newton's second law to calculate an answer:

`F = ma`

`F = "(60 kg)" xx "(1.8 m/s/s)" = "108 kgm/s/s" = "108 N"`