Forces,
Laws of Motion, Velocity
1. What is a force? (pages 374 – 377)
A. A force is a push or a pull.
B. A Newton (N) is the unit for measuring a
force like weight.
C. Net Force – the combination of all forces
acting on an object. When two or
more forces act in the same direction, add the forces. When two or more forces act in opposite
directions, add them together but one of the forces is acting in a “negative”
direction so it’s like adding positive and negative numbers.
D. Unbalanced Forces – When there is a net
force acting on an object.
Basically there is more push or pull from one direction than the
other. This means that there will
be a change in the object’s velocity in the direction of the greatest force.
E. Balanced Forces – Equal forces acting on
one object in opposite directions.
Balanced Forces do not change an object’s velocity.
2. Gravity (pages 380 – 388)
A. Gravity – Force that pulls objects
together. Gravity is caused by
mass. The more mass an object has,
the greater the gravity. The
closer objects are to each other, the more gravity will affect the objects. The more dense an object is, the more
gravity it will have.
B. Weight = mass x acceleration due to
gravity (9.8 m/s )
C. Free Fall – When the only force acting on
as object is gravity. All objects
in free fall accelerate at the same rate regardless of mass. Air
resistance can slow objects down if their shape is changed to increase air
friction. Terminal Velocity is when the downward force of gravity and
the upward force of drag are equal on a falling object.
3. Newton’s Laws of Motion (pages 389 – 397)
A. First Law of Motion – Objects at rest
stay at rest unless acted upon by an outside force. Objects in motion stay in motion unless acted upon by an
outside force.
1. Inertia – Tendency of an object to resist
a change in motion. The heavier an
object is and the faster it is moving, the more inertia it has.
B. Second Law of Motion – Force = Mass x
Acceleration
4. Speed, Velocity, and Acceleration
A. Speed = distance ÷ time (not a vector – direction doesn’t
matter)
B. Velocity
is speed in a direction. This is a vector quantity. Direction matters.
C. Acceleration is a change in
velocity. Speeding up, slowing
down, and/or changing direction.
To calculate acceleration you take the Final Velocity subtract the Initial
Velocity and divide by the total time.
5. Special Forces
A. Friction
Force
1)Friction is a force that acts opposite to a push or a pull.
When one surface interacts with
another surface.
2)
Four types of friction – Static, Sliding, Rolling, Fluid
3) Know what type of friction is being used in a situation and if you
are trying to increase or
decrease friction.
3. Elastic
Forces
1)Tension is a pulling elastic force
2)Compression is a pushing elastic force
3)Torsion is a Shear (tearing) or twisting force
