A hockey player hits a puck with his stick and changes the momentum of the puck.  For which system(s) is linear momentum conserved?  Assume no friction.  Group of answer choicesThe puck system.The puck + stick system.The puck + stick + player system.The puck + stick + player + earth system.

The conservation of linear momentum applies when no external forces are acting on the system. In this case, we are assuming no friction, which is an external force.

1. The puck system: Linear momentum is not conserved for the puck alone because the hockey stick applies a force to it, changing its momentum.

2. The puck + stick system: Linear momentum is conserved for the puck and stick system. The force exerted by the stick on the puck is internal to this system, so the total momentum of the puck and stick together is conserved.

3. The puck + stick + player system: Linear momentum is also conserved for the puck, stick, and player system. Any forces between the player, stick, and puck are internal to this system, so the total momentum is conserved.

4. The puck + stick + player + earth system: Linear momentum is conserved for this system as well. Although the player exerts a force on the earth (and vice versa) when he hits the puck, these are internal forces within the system, so the total momentum is conserved.

So, the answer is: The puck + stick system, The puck + stick + player system, and The puck + stick + player + earth system.