- Image by Scays via Flickr
There is no getting away from it, if you are going to study Architecture, Structures will come into its and the subject of Speed, Velocity and Acceleration will play a part of your studies, but for those of us who may well have pulled this into your brain at some point in the distant past, perhaps its time to review the basic principles and start to revise a little.
Unless he is travelling on a motorway , a motorist in a car can not maintain a constant speed for any length of time, traveling via ordinary roads, traffic conditions fequently cause him to change speed or stop. When deciding the time to allow for a particular journey, the motorist must therefore have some idea of the average speed at which he will be able to travel. Speed is defines as the rate of chnge of distance moved with time, thus if a journey from Birmingham to London of a 110 miles takes four hours:
Average speed = Distance/time = 27.5mph
Normally a driver notes hi actual speed at any given moment by glancing at the speedometer, but unfortunately this is not to accurate,. In order to obtain an accurate value for the speed of a vehicle at any given instant it would be necessary to measure the distance moved in a very short interval of time. This is best done by a road side observer using special apparatus to time the car over a measured distance. as long as the time interval is short, there is less likelihood that the speed will vary over te measured distance. Otherwise the value obtained will be an average speed.
Velocity is defined as the rate of change of distance moved with time in a specified direction, so if a car were travelling at a steady speed of 20mph along a perfectly straight road it would be correct to say that it had a velocity of 20mph, 30 deg east of north, or what ever direction the road is, on the other hsnd if the car were travelling round a bend with constant speed its direction of motion would be continuously changing so its velocity would also be changing, although the speed remains constant.
When the velocity of a body is changing the body is said to be accelerating. Acceleration is regarded as positive if the velocity is increasing and negative if the velocity is decreasing, so if a car is uniformly retarded and brought to rest from a speed of 60 mph in 8 sec, its some times best to revert to feet so 60mph is 88ft/sec therefore:
initisl velocity = 88ft/sec
final velocity 0 ft/sec
change in velocity = final velocity – initial velocity
= -88 ft/sec
Acceleration = Change in Velocity/time = -88/8 = -11ft/sec/sec
As stated the minus sign simply means the car is decelerating
For the none UK people reading this, you might be surprised at the imperial units, we are after all a metric nation, but we are not, my car and in fact all UK cars still uses mph , and all road signs are in Miles, although we buy petrol of diesel in Litres, go figure. But the principles of the information is correct, just change the units from Ft to Meters or Millimeters.
As for CPD, if you follow up on this and you should then I think an hours CPD is a fair claim of quality CPD under structures.