Question

A window washer pulls herself upward using the Bucket-pulley apparatus. The mass if the person plus the Bucket is 58 kg. How hard must she pull downward to raise herself slowly at a constant speed?

Answer 1

`F_"pull" = 570` `"N"`

Explanation:

If she is rising at a constant speed, then the net force on her is `0`.

The only two forces acting on her and the bucket are the (1) weight, and the (2) upward force exerted by the rope on the woman (opposite in direction and equal in magnitude to the downward pulling force she exerts on the rope).

`sumF_y = overbrace(F_"pull")^"pulling force" - overbrace(w)^("weight" = mg) = 0`

Thus,

`ul(F_"pull" = mg`

We know

• `m = color(red)(58color(white)(l)"kg"`

• `g = color(green)(9.81color(white)(l)"m/s"^2`

Therefore,

`F_"pull" = (color(red)(58color(white)(l)"kg"))(color(green)(9.81color(white)(l)"m/s"^2)) = color(blue)(ulbar(|stackrel(" ")(" "570color(white)(l)"N"" ")|)`

rounded to `2` significant figures.