The previous post in kinematics deals with one dimensional motion concept and you can browse it here.
AVERAGE VELOCITY AND AVERAGE SPEED :
Average velocity is defined as the change in position or displacement (Δx) divided by the time intervals (Δt),
v = X2 - X1/t2 - t1
where x2 and x1 are the positions of the object at time t2and t1, respectively. Here bar over the symbol for velocity is a standard notation used to indicate an average quantity. The SI unit for velocity is m/s or , although km/h is used in many everyday applications.
The average velocity can be positive or negative depending upon the sign of the displacement. It is zero if the displacement is zero. The following fugures shows the x-t graphs for an object, moving with positive velocity (Fig. a), moving with negative velocity (Fig. b) and at rest (Fig. c).
Average speed is defined as the total path length travelled divided by the total time interval during which the motion has taken place :
Average speed = Total path length/Total time interval
Average speed has obviously the same unit(m/s) as that of velocity. But it does not tell us in what direction an object is moving. Thus, it is always positive (in contrast to the average velocity which can be positive or negative). If the motion of an object is along a straight line and in the same direction, the magnitude of displacement is equal to the total path length.In that case, the magnitude of average velocity is equal to the average speed.
INSTANTANEOUS VELOCITY AND SPEED :The velocity at an instant is defined as the limit of the average velocity as the time interval Δt becomes infinitesimally small.
v = dx/dt
For uniformmotion, velocity is the same as the average velocity at all instants.
Instantaneous speed or simply speed is the magnitude of velocity.
AVERAGE VELOCITY AND AVERAGE SPEED :
Average velocity is defined as the change in position or displacement (Δx) divided by the time intervals (Δt),
v = X2 - X1/t2 - t1
where x2 and x1 are the positions of the object at time t2and t1, respectively. Here bar over the symbol for velocity is a standard notation used to indicate an average quantity. The SI unit for velocity is m/s or , although km/h is used in many everyday applications.
The average velocity can be positive or negative depending upon the sign of the displacement. It is zero if the displacement is zero. The following fugures shows the x-t graphs for an object, moving with positive velocity (Fig. a), moving with negative velocity (Fig. b) and at rest (Fig. c).
Average speed is defined as the total path length travelled divided by the total time interval during which the motion has taken place :Average speed = Total path length/Total time interval
Average speed has obviously the same unit(m/s) as that of velocity. But it does not tell us in what direction an object is moving. Thus, it is always positive (in contrast to the average velocity which can be positive or negative). If the motion of an object is along a straight line and in the same direction, the magnitude of displacement is equal to the total path length.In that case, the magnitude of average velocity is equal to the average speed.
INSTANTANEOUS VELOCITY AND SPEED :The velocity at an instant is defined as the limit of the average velocity as the time interval Δt becomes infinitesimally small.
v = dx/dt
For uniformmotion, velocity is the same as the average velocity at all instants.
Instantaneous speed or simply speed is the magnitude of velocity.
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