# How to find the average speed of a body

Average speed — size conditional, received in the settlement way. This indicator is applied to definition of necessary time of passing of the set way or course of process.

## Instruction

1. The concept "speed" defines speed of movement of an object in space or development of chemical or physical process in time. Unlike chemical processes, the movement is characterized by vector size. When calculating average speed of the movement it is about the vector module.

2. Speeds of separate points of a solid body are not equal. For example, at a point on a wheel in the place of contact with the road and at a point in the top part of a wheel the different speeds are rather expensive (a coordinate axis). Therefore when calculating average speed object of the movement is the material point.

3. At the uniform rectilinear motion the average speed on the set site of a way to a certain period is equal to v=S/t where v is the average speed of a body on the site of a way of S passed for t interval of time. If the car passed distance two hundred forty kilometers in three hours, then its average speed V on this site ways pays off so: V=240 km / 3час =80km/hour.

4. According to the first law of Newton, any physical body seeks to keep a condition of rest or the uniform rectilinear motion. In fact between these two states there is no difference. Without binding to a reference point it is impossible to understand, the body with a constant speed moves or stands still. However the external forces operating on a body interfere with preservation of such serene state. The body in the movement brakes or on the contrary accelerates, i.e. changes speed.

5. In each timepoint of t the body has the instantaneous velocity of v. Average speed of a body can be determined as private from division of the sum of such instantaneous velocities into the number of timepoints when the value of instantaneous velocity was fixed.

6. The driver of the car during passing of distance two hundred forty kilometers fixed indications of a speedometer in any timepoints: three times on a high-speed piece of route 90km/chas, once on the site of speed limit 40km/hour, once on raising of 50 km/h and one more time of 60 km/h. From these observations it is possible to calculate the average speed of the movement of the V=(90x3+40+50+60)/6=70 car. However the driver never noticed on a speedometer 70km/hour.

7. If the driver noted indications of a speedometer not in any timepoints, and strictly everyone half an hour, he could receive other values of instantaneous velocity. For example, two ninety time, on two times — fifty and sixty and once forty kilometers per hour. Then average speed on the same site of a way will be equal to about sixty three kilometers per hour. The distinction of the received results speaks about convention of the concept "average speed"

Author: «MirrorInfo» Dream Team