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# Chapter 9+10 Science

### Motion and Forces

What is motion? The state in which one object‘s distance from another is changing.
What is a reference point? A place or object used for comparison to determine if an object is in motion.
What is the International System of Units A system of measurement based on multiples of ten and on established measures of mass, length, and time.
What is a meter? The basic SI unit of length.
What is speed? The distance an object travels per unit of time.
What is average speed? The overall rate of speed at which an object moves; calculated by dividing the total distance an object travels by the total time.
What is instantaneous speed? The speed of an object at one instant of time.
What is velocity? Speed in a given direction.
What is slope? The steepness of a line on a graph, equal to its vertical change divided by its horizontal change.
What is acceleration? The rate at which velocity changes.
What is a force? A push or a pull.
What is a newton? A unit of measure that equals the force required to accelerate 1 kilogram of mass at 1 meter per second per second.
What is net force? The overall force on an object when all the individual forces acting on it are added together.
What are unbalanced forces? Forces that produce a nonzero net force, which changes an object’s motion.
What are balanced forces? Equal forces acting on an object in opposite directions.
What is friction? the force that two surfaces exert on each other when they rub against each other.
What is static friction? the friction that acts on objects that are not moving
What is sliding friction? the friction that occurs when two objects slide over each other
What is rolling friction? the friction that occurs when an object rolls over a surface
What is fluid friction? the friction that occurs when an object moves through a liquid or gas
What is gravity? a force that pulls objects together.
What is mass? the amount of matter in an object
What is weight? the force of gravity on a person or object
What is a free fall? The motion of a falling object when the only force acting on it is gravity.
What is air resistance? The fluid friction experienced by objects falling through the air.
What is terminal velocity? The greatest velocity a falling object can achieve.
What is projectile? an object that is thrown
What is inertia? The tendency of an object to resist any change in its motion.
What is momentum? The product of an object’s mass and velocity.
What is the law of conservation of momentum? The rule that in the absence of outside forces the total momentum of objects that interact does not change.
When is an object in motion? if it changes position relative to a reference point
How do scientists measure distance? SI units
How do you know an object's speed and velocity? speed = distance over time and velocity is speed and direction
How can you graph motion? slope
What kind of motion does acceleration refer to? increasing speed, decreasing speed, and changing direction
How is acceleration calculated? final speed - initial speed over time
What graphs can be used to analyze the motion of an accelerating object? speed and distance vs. time graphs
How is a force described? by its strength and its direction
How are unbalanced and unbalanced forces related to an objects motion? unbalanced forces change and balanced do not change the object's motion
What factors determine the strength of the friction force between two surfaces? how hard the two surfaces push together and the types of surfaces involved
What factors affect the gravitational force between two objects? mass and distance
Why do objects accelerate during free fall? the force of gravity is an unbalanced force
What is Newton's first law of motion? an object at rest will remain at rest and an object in motoion will remain in motion until acted upon by an unbalanced force
What is Newton's second law of motion? F=ma
What is Newton's third law of motion? if one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object.
How can you determine the momentum of an object? mass x velocity
What is displacement? how far an object has moved in relation to its starting point
What is an example of sliding friction? riding a bike and you hit the brakes to stop
What is an example of static friction? pushing a car
What is an example of rolling friction? riding a skateboard
What is an example of fluid friciton? surfing
Created by: lp1213