if things are weightless in space, why was apollo 13 affected by not having moon rocks on board?

Answer 1

Weight and Mass are different things.

Weight is a force while Mass is a physical property. When you talk about how much you 'weigh' you actually talk about your mass. If the mass of Apollo 13 differed from what had been expected forces to accelerate, slow and turn the craft would have larger effects on a lighter craft.

Answer 2

Weightlessness in the sensation that you get then something is pushing on you. You're weightless when in freefall or if you are moving at the same rate as the vehicle that you are in, but if you accelerate (either by hitting the gas or the brake in a car, for example), you'll have weight. The reason you have weight when you step on a bathroom scale is that you are constant pushing against the ground from gravity pulling you in the downward direction.

Mass, however, is a different issue as it is independent of gravity. If you were on the moon's surface, your mass would be roughly the same (depending on what you ate and removed from the body), but your weight would be one-sixth of that on earth due to the lower gravity. We tend to confuse the two as gravity is mostly constant throughout the surface of the earth (but not exact due to the fact that earth is not a perfect sphere).

In the context of the Apollo 13 mission, the thrust had to take into account the mass of the vehicle; weight is irrelevant. Less mass mean that the same thrust would push the capsule faster than is it had more mass. The change in mass required recalculation of the thrust in order to acheive the proper path and speed.

Hope that helps.

Answer 3

Weightlessness in space is actually a condition of continuous-free fall. Objects are still affected by the gravitational pull of space bodies such as the Earth. The trajectory of the return of Apollo 13 was inertial i.e. it had a trajectory determined by its weight as it rocketed away from the moon. A different weight and the gravitational pull of the Earth would interfere with the inertial trajectory and could have made it miss re-entry.

Answer 4

You are correct in that psace is weightless but you have to have the correct desent angle to enter the earths atmosphere window otherwise you would either bounce off or burn up.
The decent angle for apollo 13 was correct for a space ship which was full of rocks but since it did not land on the moon and were simply coming back they were still using the same decent angle which is now incorrect and had the apollo 13 coming in at a shallow angle!
They had to fire there engines to get back into the correct decent angle.

Answer 5

Apollo 13 was affected by lack of moon rocks on re-entry. All calculations about entering the earths atmosphere was done allowing for a few kg's of moon rock. Without it the space craft was lighter on re-entry meaning it would not have been affected by the earths gravitational field. Whilst the few kg's sounds small, when travelling at 24,000mph (about 34 times the speed of sound) and at an altitude of of about 112 miles up, a few kg's can make a big difference to its trajectory.

Answer 6

Is this some sort of way to try to say that apollo 13 was a hoax?

Well, those people are right. Weight and mass are different things. The more mass something has, the more power you need to make it move. Same goes with weight... but one can exist without the other.

Answer 7

Do not confuse weight with mass. The rocks were, more or less, weightless, but they still have mass. The mass affects how much force is needed for course corrections.

Answer 8

In weightless space no but on re-entry, when the craft comes under the influence of Earth's gravity, mass and re-entry angle are critical,
get one wrong and Tom Hanks would be out of a job.

Answer 9

a good question. without watching it again just now, I'd venture to say that it was the reentry calculations which were adversely affected. The weight wouldn't matter in space but it would in reentry.

Answer 10

IVE HEARD A THEORY THAT IT WAS A PAST UNIVERSE AND THAT THEY KEEP GROWING UNTILL THEY IMPLODE THEN EXPLODE (BIG BANG THEORY AND UNIVERSAL MASS THEORY) AND CREATE A NEW ONE