Chapter 3: Laws Governing Motion

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What is "natural motion?" What do things do if you leave them alone? Newton's First Law addresses these questions. Newton's First Law: Every object continues in its state of or of motion in a straight line with unchanging speed, unless compelled to do otherwise by forces acting upon it. "Forces" are pushes and pulls by some agent. "Uniform motion" is motion at constant in a line. Motion at constant speed in a circle (is, is not?) uniform motion. What happens when forces are exerted on an object? Newton's Second Law addresses this question. "Acceleration" is a from uniform motion. In the broad sense that we use acceleration, it may be a speeding up, it may be a slowing down or it may be a change of direction. are the causes of acceleration. (Strictly speaking, it is the "net force" which causes acceleration. But force alone does not determine how an object will accelerate. The property of an object that determines how it will accelerate in response to a given force is called the object's . Mass (is, is not?) the same thing as weight. Mass does not depend on where you measure it; weight does. Hence, they may be related things but they are not the same thing. Newton's Second Law: Forces cause objects to accelerate. For the same mass, the stronger the net force, the (lesser, greater?) the acceleration. For the same net force, accelerations are (lesser, greater?) if mass is larger. Acceleration has a direction (like force). The direction of acceleration is always the as the direction of the net applied force. An equation that represents the Second Law is: acceleration = /. Where do forces come from? Newton's Third Law gives us a partial answer to this question. Newton's Third Law: All forces result from interactions between (how many?) objects, each object exerting a force on the other. The two forces have (the same, different?) strength and act in exactly directions.

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