Why don't heavy objects fall more SLOWLY?

Buckleymanor

If I were to hit a bowling ball with a tennis bat and then a marble, both with the same amount of force won't one travell further than the other.
The marble and the bowling ball are seperated on the floor of the craft.

russ_watters

Yes....

Drakkith

In your spaceship you are accelerating them both at the same time to the same speed. Both of them are accelerating at the same rate and once you reach your maximum velocity both will be traveling at that velocity. Each one takes a different amount of force to accelerate, but since they are both on the floor of the ship at the same time they both have to accelerate at the same rate.

This is kind of similar to hitting both the bowling ball and the marble with the bat at the same time, except that hitting them with the bat has much more complicated physics come into play such as elasticity and such. Imagine you had them both sitting on a catapult at the same time and simply launched them into the air with it. Both would accelerate at the same rate to the same speed.

Buckleymanor

Yes if they were both sitting in or on the catapult together the bowling balls mass and the marble mass would each have an influence on each other and the catapult, so they would accelerate at same rate.
If they were separated and on the floor of the spacecraft, or placed on seperate seats in the front of car when the craft decelerated or the car crashed and elasticity was 'allowed' to do what it does.
They would still accelerate at the same rate to the same speed.The less massive marble would not have as much elastic effect when first accelerated as the more massive bowling ball.
Thanks.

Drakkith

No, the floor of the spacecraft is like the catapult, accelerating both equally. Same for a car.

Buckleymanor

Yes I must have been editeing at the same time you were posting thanks.

Buckleymanor

To be honest I am haveing trouble trying to understand this.
If you just had the the bowling ball on the floor of the spaceship and you accelerated it to your maximum velocity and then applied the brakes or reverse thrust and measured the distance and the speed it travelled at.
Then you repeated the same experiment with just the marble won't the distances and speeds of the two objects be different.

With respect to this question I posted. And the answer I recieved from russ_watters
If that is the case then won't it be possible to distinguish between acceleration due to gravity and acceleration due to acceleration.

Drakkith

There is no maximum velocity. Your velocity will continue to increase as long as you apply thrust. What you can do is measure the velocity relative to something else, like the Earth, for the amount of fuel you expend. Accelerating the ship with the bowling ball will get you to a lower velocity than with just the marble for the same amount of fuel.

Also, you say we should stop accelerating and apply the brakes. But that IS acceleration, it's just in the negative direction to your current vector. If you applied the same acceleration in both instances both the bowling ball and the marble would be traveling the same speed upon measurement. This is because once you reverse the thrust you are only accelerating the ship, and the motion of the ball and marble relative to the ship would be the same because the ship will accelerate the same in both cases.

And you cannot measure the distance the bowling ball or marble travel. Both will travel to the other side of the ship at the same velocity and hit the wall. Remember that in order to say that acceleration is the same as gravity we cannot "cheat" and look outside to see what is actually going on. We are forced to measure things inside the ship.

TurtleMeister

No. When the spacecraft reverses thrust, whatever objects are sitting on the floor will simply continue traveling at the velocity the spacecraft obtained before it reversed thrust (acceleration has been removed from the objects so Newton's first law applies). While the spacecraft (and the floor of course) will accelerate away from the objects (in the opposite direction).

Yes, one will travel faster than the other. But in that case you are hitting the objects separately at different times. That scenario is not analogous to the spacecraft scenario. Ask yourself this question: What would happen if you attached the bowling ball and the marble together and hit them both at the same time? That would be more analogous to the spacecraft scenario. You don't have to even attach them together, just hit them both at the same time.

Buckleymanor

Correct me if I am wrong but that would only apply if the bowling ball and marble were on board the craft at the same time.If you took the bowling ball up first and measured it's velocity it would be slower than the marbles.

Drakkith

As long as you decelerate the ship at the same rate it doesn't matter if you have one or the other or both.

Measured its velocity relative to what?

Buckleymanor

You accelerate the craft for a given amount of time with maximum thrust with just the bowling ball on board then decelerate for another measured amount of time with maximum reverse thrust.
Then repeat with just the marble on board and then compare the time it took for the marble and bowling ball to leave the floor and hit the far side of the ship.

TurtleMeister

The time would be the same. The mass of the bowling ball and marble have nothing to do with it (the time period you are talking about). What affects that time interval is the thrust of the rocket and the mass of the spacecraft (minus the bowling ball and marble). As I explained in my previous post, once the spacecraft reverses it's thrust the only thing that accelerates is the rocket. The bowling ball and marble (regardless of whether this exercise is done with them together or separate) will simply obey Newton's first law and "coast" until the other side of the spacecraft accelerates into them.

Drakkith

It would be equal. In both cases the only thing you are decelerating is the ship, not the marble or bowling ball. So applying maximum thrust would cause both to reach the other side of the ship after an equal amount of time.

Buckleymanor

Are you sure won't they have different closing velocities.
The marble and the ball would have attained different velocities with the initial acceleration.
Because you are only decelerating the ship the marble would have a greater intial velocity than the bowling ball because the ship would be lighter.

For instance if it were possible to stop the ship the craft that weighed more could not have attained the speed of a lighter craft with the same amount of thrust.

Drakkith

No, we are measuring the velocity relative to the ship, not an outside source. In such a case the velocity of the ship relative to an outside object is irrelevant, only the acceleration upon braking matters.

Buckleymanor

I don't see how that will prevent the lighter object reaching the other side of the ship more quickly.
The ship would have to accelerate at the same velocity for both which it won't becuase it's more massive with one object on board than the other.