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CA Physical Science-Motion and Forces
Physical Science Motion and Forces
47
Science
8th Grade
09/10/2009

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Cards

Term
Motion
Definition

A change in position
Term
Displacement
Definition
A description of motion that includes the distance and direction of the motion
Term
Speed
Definition
The rate of change in position
Term
Instantaneous speed
Definition
The rate of motion at any given moment
Term
Average speed
Definition

Is determined by the total distance an object travels during the total time traveled

 

s=d

   t

 

Term
Constant speed
Definition
Speed that does not vary
Term
m/s
Definition
Standard unit of SI measurement for speed
Term
Velocity
Definition
Descibes the speed and direction of a moving object
Term
Acceleration
Definition
The rate of change of velocity
Term
m/s2
Definition
standard unit of SI measurement for acceleration
Term
Positive Acceleration
Definition

occurs when velocity and acceleration are in the same direction

 

or

 

an object is increasing speed without changing direction

Term
Negative Acceleration
Definition

occurs when the velocity and acceleration of a moving object occur in different directions

 

or

 

when an object is slowing down or changing direction

Term

a=Δv

   t

 

or

 

a=vf-vi

    t

Definition
formula for calculating acceleration
Term

s=d

   t

Definition
formula for calculating speed
Term
Force
Definition
a push or a pull
Term
Balanced Forces
Definition
forces that are equal in size, but opposite in direction
Term
Unbalanced Forces
Definition

forces that create a net force that changes the velocity of an object

 

forces that are not equal in size, but opposite in direction

 

Term
Gravity
Definition

an example of a force in which one object pulls on another

 

 

Term
size and distance
Definition
two factors that determine the strength of a gravitational pull
Term
Friction
Definition
a pushing force that interferes with the motion of an object and can only occur if two objects are in contact with one another
Term
Newton's First Law of Motion
Definition

Also known as Law of Inertia

 

An object moving at constant velocity keeps moving at that velocity unless a net force acts on it

Term
Inertia
Definition
The tendency of an object to resist a change in its motion
Term
Mass
Definition
Determines the amount of inertia of an object
Term
Newton's Second Law of Motion
Definition
A net force acting on an ojbect causes the object to accelerate in the direction of the force
Term
F = m x a
Definition
Formula for calculating  force
Term
Greater Force
Definition
Greater acceleration requires ________ _______
Term
Newton
Definition
Is an SI derived unit for force that is equal to 1 kg x m/s2
Term
Gravitational pull and inertia
Definition
In the absence of air, falling objects will generally fall at the same rate due to the combined effects of ______ and ______.
Term
9.8 m/s2
Definition
Graviational acceleration for objects falling to Earth's surface is _____.
Term

Freefall

 

 

Weightless

Definition

When an object is influenced only by gravity it is said to be in ______.

 

These objects appear to be ___.

Term
Air resistance
Definition

The force air exerts on a moving object.

 

(It works in the opposite direction of the moving object)

 

(Depends on the speed, size, shape, and density of the moving object)

Term
Surface area
Definition
Air resistance can be modified by increasing or decreasing the _________ of an object
Term
Terminal velocity
Definition
The highest velocity that can be reached by a falling object
Term
Projectile
Definition

anything that is thrown or shot through air

 

has both horizontal and vertical motion at the same time

(path is curved as if falls through air)

 

Still falls to Earth at the same rate as an object that is simply dropped

Term
Centripetal acceleration
Definition
acceleration toward the center of a curved or circular path
Term
Centripetal forces
Definition
forces that act toward the center of a path
Term

Newton's Third Law of motion

 

 

Action-reaction pairs

Definition

When one object exerts a force on a second object, the second one exerts a force on the first that is equal in size and opposite in direction

 

(For every action there is an equal and opposite reaction)

 

These forces exists in opposing pairs called ____

Term
Momentum
Definition
The property a moving object has because of mass and velocity
Term
p = m x v
Definition
Formula for calculating momentum
Term
Law of Conservation of Momentum
Definition
States that the total amount of momentum of a group of objects does not change unless an outside force acts on the objects
Term

Slow down

Speed up

Change direction

Definition
What are three ways in which the velocity of an object can change?
Term
Stationary
Definition
A horizontal line on a distance-time graph indicates that an object is _____.
Term

True

 

(There is no speed less than 0 m/s)

Definition
Speed (distance-time) graphs cannot have a negative slope.
Term
Horizontal
Definition
The ________ line on a velocity-time graph indicates no acceleration (or that the object is traveling in the same direction at a constant speed)
Term
Positive slope
Definition
A velocity-time graph will indicate a positive acceleration with a _______________.
Term
Negative slope
Definition
A velocity-time graph would indicate a negative acceleration with a _______ ______.
Term
Net force
Definition
Term that refers to the sum of all the forces acting on an object
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