lecture4 - Chapter 4. Newtons laws of motion Force = mass x...

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Chapter 4. Newton s laws of motion Force = mass x acceleration l A force is that which causes an acceleration
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Classes of Forces l Contact forces involve physical contact between two objects l Field forces act through empty space ¡ No physical contact is required
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Force Force is a vector, having both magnitude and direction. The magnitude of a force can be measured using a spring scale.
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Net Force (also called total force, resultant force, or unbalanced force) l The net force is the vector sum of all the forces acting on an object F=F 1 +F 2 +F 3 +F 4 + …
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Newton s First Law l In the absence of external forces, when viewed from an inertial reference frame, an object at rest remains at rest and an object in motion continues in motion with a constant velocity ¡ This is also called the law of inertia ¡ Examples: Feel going outward when car/bus makes turns. Lean forward when car/bus stops
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Newton s First Law of Motion Inertial reference frames: Newton s first law does not hold in every reference frame, such as a reference frame that is accelerating or rotating. An inertial reference frame is one in which Newton s first law is valid. This excludes rotating and accelerating frames. How can we tell if we are in an inertial reference frame? By checking to see if Newton s first law holds!
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Newton s Second Law l When viewed from an inertial frame, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass l Algebraically, F = m a ¡ F x = m a x ¡ F y = m a y ¡ F z = m a z
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Mass m Mass is the measure of inertia of an object, sometimes understood as the quantity of matter in the object. In the SI system, mass is measured in
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lecture4 - Chapter 4. Newtons laws of motion Force = mass x...

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