free web hosting | free hosting | Web Hosting | Free Website Submission | shopping cart | php hosting

# Physics

Forces: tension, gravitational, air resistance, normal, frictional, static cling - electrostatic, protons/neutrons held together by strong nuclear, radioactive nuclei decay through weak

Newton's Laws: an object will continue in its state of motion unless compelled to change by a force impressed upon it; inertia. second - acceleration is directly proportional to strength of the total/net force and inversely to obj's mas, so F=ma. third - to every action there is an equal/opposite reaction.

Friction: parallel to surface. Both friction & normal force arise from electrical interactions btwn atoms making up obj and surface. Two kinds friction, static and kinetic/sliding. Strength depends on two things, nature of surfaces and strength normal force. nature surfaces denoted by coefficient of friction, ¥ì. One for sliding and one for static, static higher. F(friction) = ¥ìF(normal) and app. mu selected

Pulley - changes direction of tension force. Inclined plane - two components of gravity, one countering the normal force and one parallel to surface/countering friction force. Draw free-body diagrams!

Centripetal acceleration, or a(c), acceleration that makes motion in a circle [constant speed, rock being swung on string, say]; a(c) = v^2 / r. So F(c) [force keeping obj moving in circle] = mv^2 / r. Force and acceleration allus in same direction [mag times vector is vector in same direction]. If person running makes radius too small, then F(c) gets greater than static friction; slippage.

Energy: gravitational [meteor crashing to earth], elastic [stretched rubber band], thermal [oven], radiant [sunlight], mass [e=mc^2]. Force is agent of change, energy is measure of change, work is way of transferring energy from one system to 'nother. Law of Conservation of Energy, First Law of Thermodynamics.

Work: if a force F acts over a distance d, and F is parallel to d, then the work done by F is the product of force and distance: W = Fd. Work is dot-product, so F, d vectors, W scalar. W = Fdcos(angle btwn F and d). Neg work is work done against distance. If force is not constant, work done by force is given by definite integral. Work done by force as it acts from position x = x(1) to x = x(2) is W = [integral from x(1) to x(2)] F(x)dx. Graph: work done by F equals area bounded by graph of F [yes, force], x-axis, and vert lines.

Kinetic energy: K = (1/2)mv^2, energy obj poss. since it's moving. Work-Energy theorem: total work done on an object/work done by net force equals change in kinetic energy; W(total) = §QK. Scalars, both.

Potential energy: arises from obj's position, or system's config. "Stored energy." Diff types of potential energy. Gravitatitional potential energy. W(by gravity) = -F(w)h = -mgh. §QU(grav) = mgh. To use, must pick reference level for height. Differences/changes in potential energy are unambiguous [book falling changes its potential energy/some went to kinetic], even if values are relative.

Sum of an object's kinetic and potential energies is called its mechanical energy, E; E = K + U.

References: The Princeton Review's Cracking the AP Physics B & C exam