University:
Arizona State University
Course:
PHYS 102 | Introductory Physics I
Academic year:

2024
Views:

250

Pages:

5
Author:

Mohammed N.

Average and Instantaneous Speed Speed can be given as the ratio distance travelled/time taken and these both quantities are base quanties and hence as speed is derived from these both quantities it is known as a derived quantity. It's measured in m/s. NOTE: If you want to convert from m/s to Km/h you have to multiply the numerical value by 3,6. If you want to convert from Km/h to m/s you have to divide the numerical value by 3,6. Average speed is the ratio between the distance travelled and the time taken to travel it. The Average Speed Vector is defined by the formula: NOTE: Only in rectilinear motion the displacement vector module coincide with the traveled space. The instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero. Deepening In calculating the average speed, known spaces and times are used. Let's assume that it took us ten hours to get from Paris to Berlin, the distance is about 1000 km, so calculating quickly we kept an average of 100 km/h. But that doesn't mean we maintained that speed the whole time! We are simply averaging. We are also using the following formula: The Greek letter delta indicates a variation, so we can say that the distance traveled is the distance between the starting point (s2) and the arrival point (s1). We can therefore say that: The average speed does not depend on the traveled path but only on the starting position and the final position. We cannot confuse the starting and final position with the pathtravelled. Let's consider the following figure: It is clear that the displacement between points A and B is not equal to the real distance covered, it does not coincide with the trajectory followed. In any case, the difference in displacement does not change. However, one more thing must be pointed out. If I go from A to B and then from B back to A, the displacement would be zero, so the average speed would be zero! Average and Instantaneous Acceleration Acceleration is the physical quantity that expresses the rate of change of speed of an object over time. It's measured in meters per second squared. Average Acceleration is the rate at which velocity change in a defined time interval. NOTE: Particularly if v2 > v1 the acceleration is positive, if v2 < v1 the acceleration is negative (deceleration). NOTE: Particularly if v2 > v1 the acceleration is positive, if v2 < v1 the acceleration is negative (deceleration). Instantaneous acceleration is the acceleration of an object at a specific moment of time (At → 0).