Download Study Guide - Chapter 6

Chapter 6 Study Guide - Forces and Motion
Section 1 - Gravity and Motion
Galileo Galilei - Italian scientist (1500’s) that argued that the mass of an object does not affect the time
the object takes to fall to the ground
Objects fall to the ground at the same rate because the acceleration due to gravity is the same for all
objects.
1. Acceleration depends on both force and mass
2. Heavier objects experience greater gravitational force but are harder to accelerate due to their
greater mass (they have more inertia) - these forces balance out
Acceleration - the rate at which velocity changes
Acceleration due to gravity = 9.8 m/s²
Formula for calculating the change in velocity (V) of a falling object:
v - velocity
g - acceleration due to gravity (9.8m/s²)
t - time
v = g  t
Air resistance - the force that opposes the motion of objects through air
1. The amount of air resistance depends on the size, shape and speed of the object
Terminal Velocity - the constant velocity of a falling object when the force of air resistance is equal in
magnitude and opposite in direction to the force of gravity.
Free Fall - the motion of a body when only the force of gravity is acting on it.
1. Can only occur in space or a vacuum
A. a vacuum is a place in which there is not matter
Astronauts float because of free fall
Orbiting - when an object is traveling around another object in space
1. An object in orbit is always in free fall
Centripetal Force - the unbalanced force that causes objects to move in a circular path
Projectile Motion - the curved path that an object follows when thrown, launched, or otherwise projected
near the surface of Earth. It has 2 components.
1. Horizontal motion - motion parallel to the ground
A. Gravity does NOT affect the horizontal component of projectile motion
2. Vertical motion - motion perpendicular to the ground
A. Gravity pulls objects down at an acceleration of 9.8m/s²
Section 2 - Newton’s Laws of Motion
Newton’s First Law of Motion - an object at rest remains at rest, and an object in motion remains in
motion at constant speed and in a straight line unless acted on by an unbalance force.
1. Describes the motion of an object that has a net force of 0 N acting on it
2. Friction is an unbalanced force
Inertia - the tendency of an object to resist any change in motion
1. The larger the mass of an object, the larger the inertia
Newton’s Second Law - the acceleration of an object depends on the mass of the object and the amount
of force applied
A=fm
or
F=ma
Newton’s Third Law - whenever one object exerts a force on a second object, the second object exerts an
equal and opposite force on the first
1. This law can simply be stated as follows: all forces act in pairs
A. force pairs do not act on the same object
Section 3 - Momentum
Momentum - a quantity defined as the product of the mass and velocity of an object
1. The more momentum an object has, the harder it is to stop the object or change its direction
p - momentum
m - mass
v - velocity
p=mv
The Law of Conservation of Momentum - any time objects collide, the total amount of momentum
stays the same
1. Objects sticking together
A. masses of the two objects are added together. When mass changes, the velocity must
change too.
2. Objects bouncing off each other
A. momentum is transferred from one object to another object. The transfer of
momentum causes object to move in different directions at different speeds.
Conservation of Momentum can be explained by Newton’s Third Law. Because action and reaction
forces are equal and opposite, momentum is neither gained nor lost.