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8th Science-Force and Newton’s Laws
Newton’s First Law
Also known as the Law of Inertia States that an object in motion stays in
motion and an object at rest remains at rest unless acted on by an unbalanced outside force
Newton’s First Law
Inertia: a property of matter that describes the tendency of an object to resist changes in its state of motion
(The more mass an object has, the greater its inertia)
(ex: 18 wheeler vs. compact car), seatbelts,
Section 1: Newton’s Second Law
For any object, the greater the force that’s applied, the greater its acceleration will be
Relates the net force on an object (F) to the object’s mass (m) and acceleration (a)
Force, mass and acceleration are connected
Friction
Objects slow to a stop when moving freely—due to friction
The force that opposes motion between two surfaces that are touching ea/other
Amt. of friction depends on kinds of surfaces and the force pressing the surfaces together
Types of Friction:
Static Friction: friction between two surfaces that are not moving past ea/other
Sliding friction: force that opposes the motion of two surfaces sliding past ea/other
Rolling friction: friction between a rolling object and the surface it rolls on
Air Resistance:
The force on an object opposite the force of gravity when an object falls toward Earth
Effects anything that moves in Earth’s atmosphere
The amount of air resistance on an object depends on the speed, size and shape of the object
Section 3: Newton’s Third Law
Describes action/reaction pairs 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
OR: “to every action force there is an equal opposite reaction force”
Remember:
Action/Reaction forces are acting on different objects
Even though forces are equal, they are not balanced
Rocket Propulsion
Rockets use the principle that as the rocket exerts force on gases and causes them to escape out the back of the rocket, the gases exert an opposite but equal force on the rocket propelling it forward
Also: stepping out of a canoe example
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