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Chapter 2 Test Review Newton’s First Law Newton’s First Law of Motion An object at rest will remain at rest and an object in motion will continue moving at a constant velocity unless acted upon by a net force. Motion • Distance describes how far an object has moved. • Displacement is the distance and direction of an object's change in position from a reference point. Motion Motion Change in position in relation to a reference point. Reference point Motion Speed & Velocity d Speed rate of motion distance traveled per unit time s t distance speed time Speed & Velocity Instantaneous Speed speed at a given instant like on a speedometer Average Speed the total distance traveled divided by the total time of travel total distance avg. speed total time Acceleration vf - vi a t Acceleration the rate of change of velocity change in speed or direction a v f vi t a: vf: v i: t: acceleration final velocity initial velocity time Speed & Velocity Velocity speed in a given direction can change even when the speed is constant! 3 m/s north is an example Speed & Velocity Problem: A storm is 10 km away and is moving at a speed of 60 km/h. Should you be worried? It depends on the storm’s direction! Acceleration, Speed and Velocity Acceleration is the rate of change of velocity. Acceleration occurs when an object changes its speed, it's direction, or both. A change in velocity can be a change in speed or direction. Acceleration Positive acceleration “speeding up” Negative acceleration “slowing down” Newton’s First Law Newton’s First Law of Motion “Law of Inertia” Inertia tendency of an object to resist any change in its motion increases as mass increases, decreases as mass decreases Graphing Motion Distance-Time Graph A B slope = speed steeper slope = faster speed Straight (horizontal) line = no motion flat line = constant speed Single point = instantaneous speed Force Force a push or pull that one body exerts on another What forces are being exerted on the football? Fkick Fgrav Force Net Force unbalanced forces that are not opposite and equal velocity changes (object accelerates) Fnet Ffriction Fpull N W N Force Balanced Forces forces acting on an object that are opposite in direction and equal in size no change in velocity Net force of 0 Balanced Forces When two or more forces act on an object at the same time, the forces combine to form the net force The net force on the box is zero because the two forces cancel each other. Forces on an object that are equal in size and opposite in direction are called balanced forces.