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physics_chapter5notes - with it he force Chapter 5 Applying...

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with it. the force. e. or slides on a plane surface, it usually simplifies the solution to take the axes in the directions parallel and perpendicular to this surface, even en replaced by its components, so you don't count it twice. al to zero. w to relate the forces they exert on each other. e target variables. Chapter 5: Applying Newton’s Laws 5.1 Using Newton's First Law: Particles in Equilibrium Equilibrium – a body at rest or moving with constant velocity in an inertial frame of reference Ex. A hanging lamp, a suspension bridge, an airplane flying straight and level at a constant speed Newton’s First Law: When a particle is at rest or is moving with constant velocity in an inertial frame of reference, the net force acting on it—that is, the vector sum of all the forces acting on it—must be zero We most often use this equation in component form: = Fx 0 = Fy 0 1. 5.2 Using Newton's Second Law: Dynamics of Particles Dynamics – the study of the causes of motion and changes in motion = Fx max = Fy may Apparent Weight and Apparent Weightlessness When a passenger with mass m rides in an elevator with y-acceleration ay , a scale shows the passenger's apparent weight to be = ( + ) n m g ay When the elevator is accelerating upward, ay is positive and n is greater than the passenger's weight = w mg When the elevator is accelerating downward, ay is negative and n is less than the weight The extreme case occurs when the elevator has a downward acceleration = - ay g , that is, when it is in free fall. In that case, n = 0 and the passenger seems to be weightless. o An astronaut orbiting the earth in a spacecraft experiences apparent weightlessness o In each case, the person is not truly weightless because there is still a gravitational force acting 5.3 Frictional Forces Contact forces – a force between two objects (or an object and a surface) that are in direct contact with each other The normal force is one example of a contact force Friction: Page | 1
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