Chapter 4
Newton's Three Laws

Part 7


The weight of an object is the downward force exerted on it by the Earth (or any other celestial object large enough and near enough to produce a substantial gravitational interaction).


Load–force exerted perpendicularly on a supporting surface.

Example 10

The fire alarm goes off, and a 97 kg fireman slides 3.0 m down a pole to the ground floor in 1.2 s. What was the upward force exerted by the pole on the fireman?




Example 11

A passenger of mass m= 72.2 kg stands on a bathroom scale in an elevator. We are concerned with the scale readings when the cab is stationary, and when it is moving up or down.
(a) Find the general solution for the scale reading, whatever the vertical motion of the cab.
(b) What does the scale read if the cab is stationary or moving upward at a constant 0.50 m/s?
(c) What does the scale read if the cab accelerates upward at and downward at ?



Newton's Third Law Examples