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61 Cards in this Set
- Front
- Back
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force
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push or pull
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friction
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force that resists the movement of one surface past another
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Gravitational force
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force of attraction between any object and every other object in the universe
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speed
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measure of how fast an object is moving
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velocity
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speed of an object in a particular direction.
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acceleration
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rate at which velocity changes
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inertia
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tendency of an object to remain at rest or in constant motion unless a force acts on it.
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momentum
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can be used to find the force needed to stop a moving object
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Newton
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force needed to change the speed of one kilogram object by one meter per seond each second
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Forces are measured in units called
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newtons
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what 2 things should you describe about a force that acts on an object?
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If it pushes or pulls
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How can a force act if objects don't touch?
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Gravity
Electrical charge (magnets) |
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how do balanced forces affect the motion of an object
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Cause no change in motion even it an object is moving.
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How do you find the effect of forces acting on an object?
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Add the forces together
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3 types of friction
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rolling
sliding static |
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resists the motion of a rolling object
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rolling
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resists the modtion of a sliding object
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sliding
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resists the motion of an object just as it begins to move
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static
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give an example of static friction
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When you first try to slide a box across a floor.
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name ways friction is helpful
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it keeps our feet from sliding out from under us.
friction can slow us down |
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name ways friction is harmful
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can cause too much heat
can cause erosion can cause wear on shoes or tires |
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First to explain gravity
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Isaac Newton
17th Century |
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Gravity depends on
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the masses of 2 objects that exert gravitational force on each other &
the distance between 2 objects |
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The greater the mass of an object the __________ its gravitational force
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stronger
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If the distance between objects increases, the gravitaitonal pull between them ________
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decreases
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Why don't you notice the gravitational pull of your school desk?
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Both the desk & me have a low mass.
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Why do the planets stay in orbit around the sun?
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Because of the gravitational pull between the sun and planets.
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Why does the moon revolve around Earth?
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Because of the gravitational pull between earth & the moon
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what would happen to planets without gravitational pull?
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they would shoot to outer space
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what raises and lowers tides?
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Gravitational pull of the moon
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rise or fall in water level near ocean
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tide
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How many tides per day?
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Mostly
2 high & 2 low |
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Why do we notice the gravitational pull on the ocean?
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Particles move more easily in a liquid
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Why do most coastal areas have 2 high tides each day?
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As Earth spins, part of earth facing moon has a high tide and so does the opposite side of earth.
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How would you expect Earth's gravitional pull on you high in the mountains to be different that pull on a seashore.
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Less as you go up
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Motion depends on the
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frame of reference
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frame of reference
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the object the observer uses to detect motion
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3 kinds of motion
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circular (ferris wheel)
straight line (car) vibration (rapid back & forth) |
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Average speed
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distance/time
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what is the difference between instantaneous speed and average speed?
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IS- object speed at any one moment
AV- speed over distance & time |
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Acceleration occurs when
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rate of velocity changes
when it changes direction slows down & speeds up |
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What is needed to change an objects motion?
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force
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an object at rest remains at rest,
and an object in motion remians in motion at a constant speed and in a straight line, unless acted on by an unbalanced force |
Newton's First Law of Motion
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what forces slow motion?
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friction, gravity, air friction
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Newtons first law of motion is also called
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law of inertia
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amount of inertia an object has depends on its
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mass
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Greater the mass of an object, the_____ its inertia
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greater
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what does Newton's first law say about a moving object if the forces on the object are balanced?
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will remain in motion at constant speed & in straight line
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acceleration of an object depends on the mass of the object and the size of teh net force applied
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newton's second law of motion
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acceleration will increase as the
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net force increases
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equation for 2nd law of motion
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acceleration = force/mass
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newtons 2nd law shows the relationship among which 3 quanties
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mass,
size of net force direction |
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When a force is applied to an object, the object exerts on equal force in the opposite direction.
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Newton's third law of motion
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newton's 3rd law of motion also called
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law of action and reation
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for every action, there is an
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equal and opposite reaction
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an objects momentum depends of its
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mass and velocity
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total momentum before a collision equals the total mometum after collision
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law of conservation of momentum.
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A bowling ball rolls down a lane and strikes a bowling pin. Which is greater, the force of the ball on the pin or the force of the pin on the ball?
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The ball since it has a greater mass & is moving.
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Which has greater momentum, a car sitting still or a pebble rolling down a hill?
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pebble, since the car is already stopped. A force will be needed to stop the pebble.
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Which type of friction acted on a box that is moving down a ramp?
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sliding
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what force keeps planets in orbit
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gravity
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