Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: davidjh on 18/02/2010 06:51:44

Title: mass vs weight in space
Post by: davidjh on 18/02/2010 06:51:44

If one were to fire a gun in outer space, would the gun recoil at the same velocity as the bullet? Also, would a target struck by the bullet be penetrated or would it be pushed along forever at the same speed as the bullet?

David.

Title: mass vs weight in space
Post by: flr on 18/02/2010 07:30:49

Quote from: davidjh on 18/02/2010 06:51:44

If one were to fire a gun in outer space, would the gun recoil at the same velocity as the bullet?

They should not be equal.
Neglecting the energy dissipated as heat in bullet and gun, the total linear momentum (∑mv) after firing the gun should be zero.
That means the ratio between the recoil speed and bullet speed is equal with the ratio between gun mass and bullet mass. 

Quote

Also, would a target struck by the bullet be penetrated or would it be pushed along forever at the same speed as the bullet?

I guess it depends on the strength of the target. Wood, aluminum, thin sheet of iron will get penetrated. Stronger materials (like anti-bullet vest) won't get penetrated but it will move at a speed lower than of the bullet. Assuming a perfectly elastic collision, the final speed of bullet+impenetrable target is:
v_final=m_bullet/(m_bullet+M_target)*v_{bullet, initial}

Title: mass vs weight in space
Post by: Geezer on 19/02/2010 04:31:43

Must be a Sea Tiger. If there are Sea Lions, why not Sea Tigers too?