Way OT Speed conversion

[rapieper at yahoo.com (Ron Pieper)]

> 90 feet traveled in 1.5 seconds

= 60 feet/sec = 40.9090 mph (average).  Any online conversion page tells you this.

Assuming constant accelleration from a standing start, Veloctity  @ 90' = twice the average, or
81.8181 mph.

Which confirms Marc's calcs below.  But in a cheapass sort of way.

Ron


> What you are looking for is instantaneous speed which is the speed at a
> particular moment in time.
> 
> We will assume that your rocket had a constant acceleration.
> 
> Predicting the position of an object undergoing constant acceleration
> requires The formulae that we can derive from calculus concerning  constant
> acceleration and motion.
> 
> "90 feet traveled in 1.5 seconds"
> 
> Metric conversion
> 90 feet = 27.432 meter
> so,
> 27.432m in 1.5s
> 
> OK,
> x = x0 + (v0 * t) + ((1/2) * a * (t*t))
> where 
> x = distance after object accelerates for a time t
> x0 = initial distance
> v0 = initial velocity
> a = acceleration
> t = time
> 
> 
> 27.432m = 0 + 0*0 + ((1/2) * a * (1.5s*1.5s))
> 27.432m = (1/2) * a * (1.5s*1.5s)
> 27.432m = (1/2) * a * 2.25s
> a = 24.384m/sec*sec
> 
> To find the speed at 1.5s,
> v = v0 + at
> where
> v = velocity (speed)
> v0 = initial velocity
> a = acceleration
> t = time
> 
> v = 0 + (24.384m/sec*sec) * 1.5sec
> v = 36.576m/s
> 36.576 meter/second = 131.67 kilometer/hour
> or
> 36.576 meter/second = 81.81 mile/hour





 
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