Newton's Three Laws
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).
exerted perpendicularly on a supporting surface.
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?
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.
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 ?
Third Law Examples