Forces 3.5 / 5 based on 6 ratings ? PhysicsForcesASEdexcel Created by: bobCreated on: 12-05-13 11:32 Newton's 1st Law of Motion Every object remains in a state of constant velocity or remains stationary unless a resultant force acts upon it. A resultant force is needed to produce an accleration. If the resultant force is zero/no resultant force, the object will continue to move at a constant velocity/remain stationary. 1 of 5 Newton's 2nd Law of Motion Resultant force = mass x acceleration Acceleration and force are vectors Resultant force is proportional to acceleration (and moves in the same direction) 2 of 5 Newton's 3rd Law of Motion Every action has an equal and opposite reaction If body A exerts a force on body B, then body B exerts an equal and opposite in direction reaction force of the same type on body A. They are equal in magnitude, force type, and the time and line of action is the same. They act in opposite directions and on different bodies. 3 of 5 Gravity GRAVITY IS NOT A FORCE - it is acceleration Weight = downwards force Weight = mass x gravity Magnitude of acceleration in freefall = gravitational field strength Centre of gravity = the point where all the weight of an object is concentrated (it is usually in the centre of the object) 4 of 5 Diagrams A free body diagram shows all the forces acting on one object (at the centre of gravity) Weight always acts directly down Normal contact force (reaction force) acts perpendicular to the surface (ground/slope) Friction/drag forces always oppose motion. TENSION IS A FORCE Vector diagram = closed polygon if the forces are in equilibrium (resultant force = 0) Forces in equilibrium = constant velocity/stationary state (N1) Draw vector arrows from tip to tail (resultant vector = tail of first --> tip of last) 5 of 5
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