The rolling resistance for steel on steel is quite low; the coefficient of rolling friction is typically μ r = 0.002. Suppose a 180,000 kg locomotive is rolling at 10 m/s oust over 20 mph) on level rails. If the engineer disengages the engine, how much time will it take the locomotive to coast to a stop? How far will the locomotive move during this time?
The rolling resistance for steel on steel is quite low; the coefficient of rolling friction is typically μ r = 0.002. Suppose a 180,000 kg locomotive is rolling at 10 m/s oust over 20 mph) on level rails. If the engineer disengages the engine, how much time will it take the locomotive to coast to a stop? How far will the locomotive move during this time?
The rolling resistance for steel on steel is quite low; the coefficient of rolling friction is typically μr = 0.002. Suppose a 180,000 kg locomotive is rolling at 10 m/s oust over 20 mph) on level rails. If the engineer disengages the engine, how much time will it take the locomotive to coast to a stop? How far will the locomotive move during this time?
13.87 ... Interplanetary Navigation. The most efficient way
to send a spacecraft from the earth to another planet is by using a
Hohmann transfer orbit (Fig. P13.87). If the orbits of the departure
and destination planets are circular, the Hohmann transfer orbit is an
elliptical orbit whose perihelion and aphelion are tangent to the
orbits of the two planets. The rockets are fired briefly at the depar-
ture planet to put the spacecraft into the transfer orbit; the spacecraft
then coasts until it reaches the destination planet. The rockets are
then fired again to put the spacecraft into the same orbit about the
sun as the destination planet. (a) For a flight from earth to Mars, in
what direction must the rockets be fired at the earth and at Mars: in
the direction of motion, or opposite the direction of motion? What
about for a flight from Mars to the earth? (b) How long does a one-
way trip from the the earth to Mars take, between the firings of the
rockets? (c) To reach Mars from the…
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