How fast are you going?
By JonesKnows
@JonesKnows (73)
Canada
January 19, 2009 8:18pm CST
Why is it that when we measure weight its in grams, pounds, tons etc.
When we measure length its in cm, metres, inches, miles, kilometres etc.
When we measure time its in seconds, minuets, hours etc.
But when it comes to measuring speed we say 50 miles per hour, or 80 kilometres per hour? We use two different measurements for it, why?
If I'm going 80 km/hr that only tells me that if I continue at the current rate of speed for one hour I will have traveled 80km. That doest tell me how fast Im going.
2 people like this
3 responses
@owlwings (43910)
• Cambridge, England
20 Jan 09
There are only four things to measure: Mass, Length, Time and Temperature.
Everything else is expressed in terms of those units, so speed is L/T, acceleration is L/T^2. Weight actually varies depending on the acceleration due to gravity, so it depends on mass, length AND time.
Temperature, even though we measure it directly, is dependent on the energy stored in or given off by a body and energy is measured in terms of all three units as well.
If your speed is 80 km/hr (or 50 mph), that IS how fast you are going. If it takes you an hour to travel 80 km, your speed may vary from 0 kph to something more than 80 kph because you accelerate and decelerate as you drive. In that case your AVERAGE speed is 80 kph though your speed at any instant may not be.
@JonesKnows (73)
• Canada
20 Jan 09
Why cant they give low speeds their own measurement like they do for high rates of speed?(eg. mach 1)
@owlwings (43910)
• Cambridge, England
20 Jan 09
Mach 1 represents the speed of sound in air and that varies depending on temperature, pressure and humidity. It's not a fixed speed.
It's useful in aeronautics because it's the speed an aeroplane has to travel to just keep up with the sound that it's generating. If it travels at the speed of sound, it builds up a big standing pressure wave at its leading edges. If it goes faster, it breaks through that pressure wave, something like popping a bubble.
@cobrateacher (8432)
• United States
20 Jan 09
Welcome to myLot, Jones.
If that doesn't tell you, what would indicate how fast you're going? I've tried and tried, but I can't htink of another way that works at all.
