后座动量应该和弹丸加燃气的动量大致相等。
Free Recoil momentum = (Wr/g) * Vre
= (250,000 / 32.174) * 37.236
= 289.33 x 10^3
The Broadside Momentum for 9 projectiles can now be calculated as follows:
9发齐射的动量：
Broadside Momentum = 9 * (momentum of projectile + momentum of propellant gasses)
= 9 * (209.80 x 10^3 + 79.54 x 10^3)
= 2.60 x 10^6
Using Greg's formula, the velocity of an Iowa firing a 9-gun broadside can be recalculated as follows:
计算IOWA在齐射后的速度：
Mass of broadside * Velocity of broadside = Mass of ship * Velocity of ship
齐射质量×速度＝船质量×船速度
As the Mass of broadside * Velocity of broadside term is equivalent to Broadside Momentum, this formula can be restated as follows:
因为齐射质量×速度等于之前计算的齐射动量，推得：
Broadside Momentum = Mass of ship * Velocity of ship
齐射动量＝船质量×船速度（横移速度）
Solving for the velocity of the ship and using the above calculated momentum figures:
计算：
Velocity of ship （船横移速度）= Broadside Momentum / [Mass of ship] （齐射动量/船质量）
= 2.60 x 10^6 / [58,000 * (2,240 / 32.174)]
= 0.64 fps
So, the ship's velocity ON ICE with the guns firing at zero degrees elevation would be about 7.7 inches per second rather than the 6 inches per second calculated above. When one considers that any sideways motion of the ship through water is actually resisted by the wall created by the hull of the ship, whose wetted surface is about 860 feet long and 38 feet deep, then it can be easily understood that Dick Landgraff's comment above, "theoretically, a fraction of a millimeter," is closer to the truth.
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