2. Freely falling
If air resistance is
disregarded, all objects
dropped near the surface
of a planet fall with the
same constant
acceleration. This
acceleration
is due to gravitational
force, and the motion is
referred to as free fall.
3. Freely falling
The acceleration due to
gravity is denoted with
the symbols ag
(generally)
or g (on Earth’s surface).
The magnitude of g is
about 9.81 m/s2.
4. Acceleration is constant during upward
and downward motion
In the photograph on the
left, the upward
displacement of the ball
between each successive
image is smaller and
smaller until the ball stops
and finally begins to move
with an increasing
downward velocity, as
shown on the right.
6. A robot probe drops a camera off the rim of a 239 m
high cliff on Mars, where the free-fall acceleration is
−3.7 m/s2.
a. Find the velocity with which the camera hits the
ground.
b. Find the time required for it to hit the ground.
7. A flowerpot falls from a windowsill 25.0 m above the
sidewalk.
a. How fast is the flowerpot moving when it strikes the
ground?
b. How much time does a passerby on the sidewalk
below have to move out of the way before the
flowerpot hits the ground?
8. A tennis ball is thrown vertically upward with an
initial velocity of +8.0 m/s.
a. What will the ball’s speed be when it returns to its
starting point?
b. How long will the ball take to reach its starting
point?
9. Jason hits a volleyball so that it moves
with an initial velocity of 6.0 m/s straight
upward. If the volleyball starts from 2.0 m
above the floor, how long will it be in the
air before it strikes the floor?
