Week3a - FIRST YEAR PHYSICS FIRST PHYS141 LECTURER: Dr....

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FIRST YEAR PHYSICS FIRST YEAR PHYSICS PHYS141 LECTURER: Dr. Carey Freeth Rm 4.110 Ph. 02 42214798 Email: carey_freeth@uow.edu.au FORCES are what move and accelerate objects. Types of forces a) Contact Forces (require contact) - Pushing - Pulling b) Field Forces (do not require contact) - Gravity - Electrostatic
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The fundamental relationship of the motions of particles to the forces that cause them is expressed by Newton’s laws of motion: 1. A body remains at rest or moves with a constant velocity unless acted upon by an unbalanced external force. (The law of inertia). 2. The acceleration of a body is inversely proportional to its mass and directly proportional to the resultant external force acting on it: 3. The forces that two bodies exert on one another are equal in magnitude and opposite in direction. _____________________________ r F = r F net ! = m r a Inertia is the tendency for any object to resist change in its state of motion. A body at rest tends to stay at rest and one in motion tends to stay in motion DEMO
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The acceleration of a body is inversely proportional to its mass and directly proportional to the resultant external force acting on it: From Newton’s second law it is seen that force is a vector, it has a magnitude and direction. The NET RESULTANT FORCE is the vector sum of all forces acting on a body. Precise definitions of force and mass can be developed from these laws. A force can be found quantitatively by measuring the acceleration that it exerts on a standard reference body. The International standard body is a cylinder of platinum having a mass of 1 kg, the SI unit of mass. Once the force has been calibrated, then other forces can be measured and investigated in the way they combine. Masses can be compared by measuring the accelerations of different objects produced by the same force. __________________________________________________ Unit of Force If 1 kg is taken to be the mass of the standard body, the corresponding unit of force that produces an acceleration of 1 m/s 2 is the newton (N).
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Week3a - FIRST YEAR PHYSICS FIRST PHYS141 LECTURER: Dr....

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