# Velocity

views updated May 18 2018

# Velocity

Velocity, in physics, is defined as the time rate of change of the position of a body. Mathematically, velocity is a vector quantity having direction as well as magnitude (length). Speed, on the other hand, is a scalar quantity that has only magnitude. An object moving with constant velocity (v) during a particular period (t) along a straight line has a certain displacement (s). This motion is described with the equation: v = s/t.

For example, an automobile runs at a constant rate for two hours and travels north for 120 miles on a straight stretch of road. Its velocity contains both a directional and a magnitude component. Its direction is north and its magnitude (speed) is v = s/t = 120 miles/2 hours = 60 miles per hour. As seen, the magnitude of velocity is expressed in units such as miles per hour or meters per second when describing motion along a straight or curved path. The International System of Units (SI) for velocity is meters per second.

A body sometimes does not maintain constant speed during a trip. When this happens, an average velocity can be calculated. One of the simplest ways to calculate average velocity (vav) is to add the initial velocity (vinitial) and the final velocity vfinal and divide by two; that is, vav = (vinitial + vfinal)/2.

For example, an automobile that travels at vinitial = 55 miles per hour for the first half of a trip but then speeds up to vfinal = 65 miles per hour for the last half of the trip, would have an average velocity of (55 miles per hour + 65 miles per hour)/2 = 60 miles per hour (that is, assuming the automobile is traveling in the same direction for the entire time, so that its directional component remains the same).

A body that is rotating about an axis has angular velocity. Angular velocity is also a vector quantity and is expressed as units of angular rotation (w) per unit of time (t) such as revolutions per minute or radians per second.

For example, if a rider on a carousel goes around once every 30 seconds, then the rider makes one 360° revolution every 30 seconds. Thus, v = w/t = 360°/30 seconds = 12%deg; per second. The SI unit for angular velocity is radians per second (where 360° equals 2π), but other units are also commonly used such as revolutions per minute (rpm).

# velocity

views updated May 18 2018

velocity (symbol v) Rate of motion of a body in a certain direction. Velocity is a vector (magnitude and direction), whereas speed, which does not specify direction, is a scalar. Velocity can also be a measurement of how quickly an object changes its position in a given direction. An object's velocity can be found in the same manner as speed, by dividing the distance s it has travelled by the time t taken, and this is expressed as v=s/t and given in metres per second (ms-1) or kilometres/miles per hour. Velocity is then stated, for example, as ‘60kph/37mph eastward’. Positive and negative values to represent movement in opposite directions can be shown on both a velocity-time graph and a displacement-time graph (movement from a fixed position).

# velocity

views updated May 18 2018

ve·loc·i·ty / vəˈläsətē/ • n. (pl. -ties) the speed of something in a given direction: the velocities of the emitted particles. ∎  (in general use) speed: the tank shot backward at an incredible velocity. ∎  (also ve·loc·i·ty of cir·cu·la·tion) Econ. the rate at which money changes hands within an economy.

# Velocity

views updated May 29 2018

# Velocity

Velocity is the time rate of change of the position of a body. Mathematically, velocity is a vector quantity having direction as well as magnitude. Speed, on the other hand, is a scalar quantity which has only magnitude. The magnitude of velocity is expressed in units such as miles per hour or meters per second when describing motion along a straight or curved path. A body which is rotating about an axis has angular velocity. Angular velocity is also a vector quantity and is expressed as units of angular rotation per unit of time such as revolutions per minute or radians per second.

# velocity

views updated Jun 08 2018

velocity swiftness of motion XVI; rapidity of operation XVII. — (O)F. vélocité or L. vēlōcitās, f. vēlox swift, rapid; see -ITY.

# veloce

views updated May 14 2018

veloce, velocemente (It., superlatives velocis- simo, velocissimamente). With speed, very fast.