3 physics problems!? CHALLENGE?

Question by mathstinks: 3 physics problems!? CHALLENGE?
1. to simulate the apparent weightlessness of space orbit, astronauts are trained in the hold of a cargo aircraft that is accelerating downward at g. Why will they appear to be weightless as measured by standing on a bathroom scale, in this accelerated frame of referenc? is there any diff between their apparent weightlessness in orbit and in the aircraft?
2. a cartoon shows the toupee coming off the head of an elevator passenger when the elevator rapidly stops an upward ride. can this really happen without the person being tied to the floor of the elevator? explain.
3. calculate the maximum acceleration of a car that is heading up a 4 degree slope (with the horizontal) under the road condition of rubber on dry concrete (mu = 1) assume that only half the weight of the car is supported by the two drive wheels and that the static coefficient of friction (1) is involved (tires aren’t allowed to slip during acceleration)

PLEASE HELP!!!!!!!! please!!

Best answer:

Answer by Harry
1. When you are in a vehicle accelerating downwards at g, and you are accelerating also downwards at g due your mass or weight, there is no interaction between you and the vehicle, that’s why the scale shows you’re weightless.
It is not quite the same as you’re in orbit or space, in orbit the gravity force is balanced by the centrifugal force due to the orbital movement, and in space there is practically no gravity.
2. When you move up at a certain speed , and suddenly elevator is stopped you still have same the speed at that very moment, this meant you are lifted from elevator’s floor until the gravitational force stop your move and brings you back to the elevator’s floor. In real life this won’t happen because speed is relatively slow and there is no chance to stop elevator suddenly (speed=0)
3. The normal force to the street from drive wheels = 0.5 * mg * cos 4
then static friction force max = mu * 0.5 * mg cos 4 = 1 * 0.5 * mg * 0.998 = 0.4988 mg
0.4988 mg = m*a
a = 0.4988 *9.81 = 4.893 m/sec**2

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