1.Do the two objects reach the
ground at the same time? If no,
which falls to the ground first?
2.What factors affect the fall of the
object? Justify your answer.
Galileo was interested in
the behavior of falling
objects. He knew that as
falling objects go down,
they increase their speed
as they go down. This
change in speed is
Galileo proved that regardless of
their masses and air resistance,
two objects dropped
simultaneously will reach the
ground at the same time. He also
discovered that objects fall with
Galileo and the leaning Tower of Pisa Free Fall
What is uniform or constant acceleration?
For Galileo, constant acceleration means moving with
increasing velocity evenly proportionate to time. The following
graphs show the comparison between the motion of objects
with constant velocity and object with constant acceleration.
After every second, a ball rolling down an inclined plane
increases its speed by the same value. He then observed
• acceleration of the rolling ball increases as the
inclined plane becomes steeper.
• When the inclined plane was positioned vertically, the
rolling ball has maximum acceleration.
To have a constant velocity, an object must have a
constant speed in a constant direction. If an object
maintains a constant or a uniform change in its
velocity in a given time interval along a straight line,
then it is said to have a constant acceleration.
Galileo rolled balls down inclined planes and observed and
recorded the gain in speed as the rolling continued.
• On downward-sloping planes, the force of gravity increases a ball’s speed while on
an upward slope, the force of gravity decreases a ball’s speed.
• With regards to the ball rolling on a level surface, it neither slows down nor speeds
up. It maintains a constant speed. Galileo reasoned that a ball would move forever if
it is in a horizontal motion.
• A moving object needs no force to keep it moving. when friction is absent. Such a
ball would remain in motion all by itself of its inertia.