momentum conserved during inelastic collision?

[dadasolee]

When child/sled system collides with a log (inelastic collision), is momentum conserved?

The answer key to BR seems to make a contradiction, saying that during the collision momentum is conserved and KE not conserved, whereas once the log comes almost immediately to a full stop, neither momentum nor KE is conserved. What's going on?

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[Bruinsfinalfour]

When child/sled system collides with a log (inelastic collision), is momentum conserved?

The answer key to BR seems to make a contradiction, saying that during the collision momentum is conserved and KE not conserved, whereas once the log comes almost immediately to a full stop, neither momentum nor KE is conserved. What's going on?

Momentum is conserved during all collisions unless an external force is present (friction, air resistance..). In this case the log comes to a stop due to friction and momentum is not conserved