Download distance d speed = or: s = time t final velocity

Integrated Science
Chapter 7 Notes
Section 1: Motion
• Speed – distance traveled divided by the time interval during which the motion occurred
⇒ To find speed you must measure two quantities: distance traveled by an object and the time
required to travel that distance.
⇒ Units for speed include meters per second (m/s) and kilometer per hour (km/hr)
⇒ Speed is calculated as distance divided by time:
speed =
•
•
distance
d
or: s =
time
t
Velocity – the quantity describing both speed and direction
Momentum – a quantity defined as the product of an object’s mass and its velocity
⇒ The momentum of an object depends on its mass and velocity.
‰ A tractor/trailer has a greater momentum than a car traveling at the same velocity
‰ A fast moving train has a greater momentum than a slow moving train
⇒ The law of conservation of momentum:
The total amount of momentum in a system is constant
Section 2: Acceleration and Force
• Acceleration – change in velocity divided by the time interval in which the change occurred
acceleration =
•
•
•
final velocity - intial velocity
Δv
or a =
time
t
⇒ Acceleration can be a positive or negative value. Positive acceleration indicates that the object’s
velocity is increasing, while negative acceleration indicates that the object’s velocity is
decreasing.
Force – the cause of acceleration, or change in an object’s velocity.
⇒ Usually many forces act on an object at the same time. The net force, the combination of all of
the forces acting on an object, determines whether the velocity of the object will change.
⇒ Balanced forces – forces acting on an object that combiner to produce a net force equal to zero
⇒ Unbalanced forces – forces acting on an object that combine to produce a net nonzero force
Friction – the force between two objects in contact that opposes the motion of either object
⇒ Frictional force varies depending on the surfaces in contact
⇒ Air resistance is a form of friction
⇒ The amount of air resistance on an object depends on its size and shape as well as son the
speed with which it moves
Gravity – the force of attraction between two particles of matter due to their mass
⇒ Technically, gravity is not a force, it is the rate of acceleration of an object in free-fall in a vacuum
⇒ All objects, regardless of mass, have the same acceleration when free-falling in a vacuum
acceleration due to gravity (g) = 9.8
m
s2
⇒ Mass and distance affect the force due gravity
‰ The greater the mass of an object, the larger the force due to gravity that object exerts on
other objects
‰ The greater the distance between the objects, the smaller the force due to gravity between
the objects
Section 3: Newton’s Laws of Motion
• Newton’s First Law:
An object at rest remains at rest and an object in motion
maintains its velocity unless it experiences an unbalanced force
•
⇒ Inertia – the tendency of an object to remain at rest or in motion with a constant velocity
‰ The larger the mass of an object, the greater its inertia
Newton’s Second Law:
The unbalanced force acting on an objects equals
the object’s mass times its acceleration
⇒ Newton’s Second Law describes the relationship between mass, force, and acceleration:
force = mass x acceleration, or: F = ma
kg m
⇒ Force is measured in newtons (N): 1N = 1
s2
⇒ Free-fall – the motion of a body when only the acceleration due to gravity is acting upon it
⇒ Weight – The force with which gravity pulls on a quantity of matter:
weight = mass x acceleration due to gravity, or: W =mg
•
⇒ Weight is different from mass
‰ Mass is the amount of matter an object has and can only be changed when matter is added
or taken away from the object. Weight is the attractive force between objects, and varies with
mass and distance.
Newton’s Third Law:
For every action force, there is an equal and opposite reaction force
⇒ According to this law, forces occur in pairs, and these forces occur at the same time
‰ The most visible example of this law how rockets work. The push of the gases formed by
burning fuel is matched by an equal and opposite push which accelerates the rocket