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Chapter 4Dynamics: Newton’s Laws of Motion1Units of Chapter 49Force9Newton’s First Law of Motion9Mass9Newton’s Second Law of Motion9Newton’s Third Law of Motion9Weight—the Force of Gravity9Free-Body Diagrams9Problem Solving—A General Approach24-1 ForceA forceis a pushor pull. An object at rest needs a force to get it moving; a moving object needs a force to change its velocity.34-1 ForceForce is a vector, having both magnitudeand direction. The magnitude of a force can be measured using a spring scale.4
4-1 ForceIdentifying forces…(a) Non-contact forces… arise between two objects even though they do not touch each other.–Gravity. Weight–Electromagnetic forces.–Nuclear interaction forces.(b) Contact forces … arise when two objects touch each other.–Pushor pull.–Tension…act along the length of a rope.–Normal forces … are perpendicular to a surface.–Frictional forces… are parallel to a surface. 56Isaac Newton (1642 – 1727)74-2 Newton’s First Law of MotionThis is Newton’s first law, which is often called the law of inertia:Every object continues in its state of rest, or of uniform velocity in a straight line, as long as no net force acts on it.Frepresents the force applied by the person and Ffrrepresents the force of friction.8