Forces in Motion
Chapter 6 Section Reviews
Pg 144 #1-4; pg 149 #1-3; pg
153 #1-3
Pg 144 #1-4
1. How does air resistance affect the
acceleration of falling objects?
Air resistance slows or stops
acceleration of falling objects.
2. Explain why an astronaut in an orbiting
spaceship floats.
An astronaut in an orbiting spaceship floats
because both the astronaut and the spaceship
are in free fall. Since both fall at the same rate,
the astronaut floats inside. The astronaut has
not sensation of falling.
Pg 144 #1-4 (cont.)
3. How is an orbit formed?
An orbit is formed by combining two
motions: a forward motion and free fall
toward Earth. The path that results is a
curve that matches the curve of Earth’s
surface.
4. Think about a sport you play that involves a
ball. Identify at least four different instances in
which an object is in projectile motion.
Basketball – a player jumping to dunk the ball, a
ball passed from one player to another, a ball
shot toward the basket, a ball bounced on the
floor.
Pg 149 #1-3
1. How is inertia related to Newton’s law of
motion?
Newton’s first law says that matter resists any
change in motion. Inertia is the tendency of
objects (matter) to resist changes in motion.
Newton’s first law is also known as the law of
inertia.
2. Name two ways to increase the acceleration of
an object.
You can increase the acceleration of an object
by increasing the force causing the
acceleration or by reducing the object’s mass.
Pg 149 #1-3 (cont.)
3. If the acceleration due to gravity were
somehow doubled to 19.6 m/s/s, what
would happen to your weight?
If the acceleration due to gravity
were doubled, your weight would
double. This is because of Newton’s
second law: F = ma. Weight is the
force due to the acceleration on
mass. If acceleration is doubled and
mass remains the same, the force
(weight) is doubled, too.
Pg 153 #1-3
1. Name three action and reaction force
pairs involved in doing your homework.
Name what object is exerting and what
object is receiving the forces.
Using a pencil or pen (action: hand
pushing on pencil; reaction: pencil
pushing back on hand OR action:
pencil pushing on paper; reaction:
paper pushing on pencil).
Pg 153 #1-3 (cont.)
2. Which has more momentum, a mouse
running at 1 m/s north or an elephant
walking at 3 m/s east? Explain your
answer.
The elephant has both a
greater mass and greater
velocity.
Pg 153 #1-3 (cont.)
3. When a truck pulls a trailer, the trailer
and truck accelerate forward even though
the action and reaction forces are the
same size but in opposite directions. Why
don’t these forces balance each other out?
The action and reaction forces do not
balance each other because the forces are
acting on two different objects. Because
they act on two different objects, you
cannot combine them to determine a net
force.