Posted by Jen on Wednesday, February 22, 2012 at 6:33pm.
An astronaut is inside a rocket that is blasting off vertically from the launch pad. You want this rocket to reach the speed of sound (331 m/s) as quickly as possible, but you also do not want the astronaut to black out. Medical tests have shown that astronauts are in danger of blacking out for an acceleration greater than 4g.
1.) What is the maximum thrust the engines of the rocket can have to just barely avoid blackout? Start with a freebody diagram of the rocket.
2.) What force, in terms of her weight W, does the rocket exert on the astronaut? Start with a freebody diagram of the astronaut.
3.)What is the shortest time it can take the rocket to reach the speed of sound?

Physics  Damon, Wednesday, February 22, 2012 at 8:37pm
forces on rocket are weight down mg
and
force up + T thrust
so
T  m g = m a = 4 m g
T = 5 m g
Force up on astronaut = F
now let M = mass of astronaut
weight of astronat down = Mg = W
so
F  W = M(4g)
F = W + 4 W = 5 W
a = 4 g = 4*9.81
v = 4 * 9.81 t = 331
t = 331 /(4*9.81)