Saturday, October 22

Pre Launch

We are at the local common to blast off Mercury,  Excalibur, and Tomahawk and I am 11 years old all over again.  The thrill of seeing these babies accelerate to 1000 ft/ sec. is , well, magic.  The Mercury by far the best launch : we put her up seven times and she falls to bits: first , the antennae needle gone, then the red tower, followed by a fin and finally, on the last launch, she goes up 250 feet then does a slow U turn for the ground , parachute ejecting on impact , tube snapped in two. I will fix her up new. The Tomahawk, meanwhile, my lightest , goes highest: : a C8 engine jammed in the rear takes her 2,000 feet : the parashoot fails to employ so that is that.  The Excalibur loses a couple fins and she, too, back to the shop. A top-ten day.

From some math book : A model rocket is fired vertically upward from rest. Its acceleration for the first three seconds is a(t)=60t, at which time the fuel is exhausted and it becomes a freely “falling” body. Fourteen seconds after the fuel is exhausted, the rocket’s parachute opens, and the (downward) velocity slows linearly to -18 ft/sec in 5 seconds. The rocket then “floats” to the ground at that rate. Find the position function s and the velocity function v for any time t, then sketch the graphs of s and v.