Glossary - 1 Mechanics

What appears below is an informal glossary of terms used in a high school physics course. On the one hand, you are not likely to be tested on your knowledge of these terms (there will not be a question asking you to define these terms). On the other hand, your intimate knowledge of these terms may make a significant impact on your test scores.

 VECTOR- a physical quantity that can only be defined completely by giving it a magnitude (or size) and a spatial direction. Examples might include 5 m due north, 3 m / s that-a-way, or 10 m/s/s downward.

 SCALAR - A physical quantity the can be defined adequately by giving a magnitude (size) only. Spatial direction is not required. Time is a scalar; so too is work and energy and power.
 DISPLACEMENT- The straight line distance from point A to point to a point B. A VECTOR QUANTITY measured in m and km mostly; occasionally measured in feet or miles. Note that the displacement on a running track from a starting point A and continuing one lap around the track, ending at point B (which in this example is on top of A) is ZERO.
 DISTANCE TRAVELED - This is path length, a meander, without regard to direction. DISTANCE TRAVELED is a SCALAR quantity measured in m and km mostly; occasionally measured in feet or miles. Note that the distance traveled on a running track from a starting point A, and continuing one lap around the track, ending at point B (which in this example is on top of A) is 400 m on a standard track
 TIME - operationally defined as a sequence of events. A SCALAR quantity measured mostly in seconds and hours
 SPEED - DISTANCE TRAVELED divided by TIME. This is a measure of how fast an object is moving, without regard to direction. SPEED is a SCALAR quantity and is the magnitude portion of VELOCITY A speedometer measures speed. Speed is measured in m / s, and km / hr and occasionally ft/s and mi / hr

 VELOCITY - DISPLACEMENT divided by TIME. VELOCITY is a VECTOR quantity.his is a measure of how fast an object is moving, but noting both magnitude (how big is it) as well as direction. VELOCITY is measured in m / s, and km / hr and occasionally ft/s and mi / hr
 ACCELERATION - The change in VELOCITY during a change in TIME. ACCELERATION is a VECTOR quantity measured in m/s/s and km/hr/s and occasionally in ft/s/s and mi/hr/s.

 Other velocities Initial velocity - (a.k.a Vo )the velocity of an object at the beginning of a trip. For an object launched vertically, Vi is the velocity of the object immediately after leaving the thrower's hand Final velocity - The velocity of an object at the end of a trip. For an object falling from a high place, Vf is the velocity of the object just before it hits the ground. Average speed - total distance traveled divided by total elapsed time. Terminal velocity - When an object is released from a high place, gravity causes the object to accelerate downward. As it accelerates, its velocity increases downward. Air resistance causes the net downward acceleration to be diminished. until it reaches Zero. After this moment in time, Fnet goes to Zero, acceleration goes to zero. The object now falls at the same rate the rest of the way down. This is known as terminal velocity; for objects under the influence of the Earth's gravity and atmosphere, terminal velocity is of the order of 54 m/s (= 176 ft/s or 120 mi/hr)

Forces

 Applied Force - ( a.k.a. FA) A push or pull that can produce or prevent motion.
 Gravity (a.k.a. Fg) An intrinsic force wherin every object with a mass shares a mutual attraction with every other object with a mass. While wew are under the influence of gravitational attraction from every other object in the universe, our immediate neighborhood is dominated by the Earth's gravitational field. The gravitational field intensity vector here on the Earth has a numerical value of 9.8 m/s/s and is directed toward the center of the planet.
 Normal Force (a.k.a FN). When an object is placed on a surface, the force of gravity pulls down on the object. For the object to remain in place, an upward force, perpendicular to the surface and pointing away from the surface, is supplied by the surface. When crossing a bridge. the bridge holds if it can muster a sufficient upward force to equalize gravity
 Frictional Force (a.k.a.Ff) A contact for that opposes or tends to oppose motion. We find that the ratio of frictional force to the Normal force is a constany u. Otherwise, Ff = u FN. The values of u are close to zero when therer is no friction, higher values when friction comes into play

 Tension (a.k.a. Ft). When a force is applied to an object by attaching a string to it. Strings are intended to pull on objects rather than push on them..
 Centripetal Force (from Latin centri- center; peto retere to seek.) Consider a cart moving left to right at constant speed. To make the object move faster, we push to the right. To slow the object, we push to the left. If the force is applied at right angles to the motion, the speed is neither increased nor decreased. It is the DIRECTION that has changes. If the direction of the applied force is change so as to be alwaysa at right angles to the velocity vector, the path is a circle.
 Centrifugal force (from the Latin centri- center; fugo, fugere to flee. Ostensibly, a force necessary to keep an object moving in a circular path. Centrifugal force does not exist and any evidence to the contrary can usually be traced to a mis-application of Newton's first law of motion. Yes, there exists a laboratory apparatus called a centrifuge. So what?