My spaceship is floating freely in space (let's just say for arguments sake that it is not in any gravitational fields and can detect no apparent motion). The total

My intention is to "throw" a 1kg "brick" of matter out the back of the ship with a velocity of 25km/sec (we'll ignore the mechanism for this unless you tell me that we cannot).

According to Newton there should be an equal and opposite reaction. Literally, my spaceship will move in the opposite direction from the brick. ie. it will be accelerated by an amount equal to the mass and velocity of the brick.

How would one work out the acceleration of the spaceship?

Is it really as simple as this?

Force = brickmass x acceleration

25000n = 1kg x 25000m/s<sup>2</sup>

therefore

force / shipmass = acceleration

25000n/1000000kg = 0.025m/s<sup>2</sup>

The ship will be accelerated by 0.025m/s<sup>2</sup> for one second.

Or do I have to allow that my spaceship is now 1kg less massive?

therefore

25000n/999999kg = 0.025000025m/s<sup>2</sup>

I know the difference is neglibible but I'm not sure which is correct (if either).

Thanks in advance for any comments, or related ideas.

kind regards

Paul

**mass**of the spaceship is 1,000,000kg.My intention is to "throw" a 1kg "brick" of matter out the back of the ship with a velocity of 25km/sec (we'll ignore the mechanism for this unless you tell me that we cannot).

According to Newton there should be an equal and opposite reaction. Literally, my spaceship will move in the opposite direction from the brick. ie. it will be accelerated by an amount equal to the mass and velocity of the brick.

How would one work out the acceleration of the spaceship?

Is it really as simple as this?

Force = brickmass x acceleration

25000n = 1kg x 25000m/s<sup>2</sup>

therefore

force / shipmass = acceleration

25000n/1000000kg = 0.025m/s<sup>2</sup>

The ship will be accelerated by 0.025m/s<sup>2</sup> for one second.

Or do I have to allow that my spaceship is now 1kg less massive?

therefore

25000n/999999kg = 0.025000025m/s<sup>2</sup>

I know the difference is neglibible but I'm not sure which is correct (if either).

Thanks in advance for any comments, or related ideas.

kind regards

Paul

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