FUNDAMENTALS OF MECHANICS WAVERLY LABS JEREMY SHUM WHAT
FUNDAMENTALS OF MECHANICS WAVERLY LABS : JEREMY SHUM
WHAT IS ENGINEERING MECHANICS? • The objective of engineering mechanics is to avoid “big scenes” such as a car falling over a ledge, luggage boxes in a vessel tipping over, etc • Engineering mechanics is an “applied” science (which is distinct from a “pure” science”), dealing with physical phenomena • Applied mechanics involves applying physics and mathematics. The three branches include: • Rigid-body mechanics • Deformable-body mechanics • Fluid mechanics
FUNDAMENTAL MECHANIC CONCEPTS • Statics deals with the effects of forces on the equilibrium of physical bodies • That is, Newton’s first law that an object in motion will move with constant velocity unless acted by a nonzero net force • Dynamics deals with the effects of forces on the motion of physical bodies • That is, change in velocity or direction • Particle is a theoretical single point which has a mass but no size. • An assumption is thus made so that the geometry (size) of a body is not considered. • Rigid body is a theoretical finite-sized mass, involving the combination of a large number of particles (e. g. the planet earth). • An assumption is thus made so that the material properties is not considered • Yes, unlike the particle, the geometry (size) is considered • Free-body diagram is an analytical method which involves: • Isolating an object to be studied from its surrounding objects • Illustrating the forces acting on the object
NEWTON’S LAW OF GRAVITATION • The fairytale goes that Newton sat under an apple tree and an apple fell on his head, causing him to think of the law of gravitation. • The law of gravitation is that 2 particles of mass M and m are mutually attracted with equal and opposite forces, with the magnitude: • Also, Newton’s 2 nd law of gravitation: • Thus, mass is the measure of how much “material” is in object • Weight is the measure of the gravitational force exerted by the material in a gravitational field • • Thus, mass is constant in whatever gravitational field Note weight (force) depends upon the gravitational field, for example the moon has less gravitational acceleration, so there will be less force
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