MOMENTUM
3 marks · NormalDescribe and explain what happens to the momentum of two ice skaters who push off from one another on frictionless ice. Use the principle of conservation of momentum.
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Must show: Total momentum before zero, Two skaters move in opposite directions, Total momentum after also zero
Common mistakes: Omitting mention of direction or total being unchanged
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Marking points
B1 · 1 mark · States total momentum is zero before push.
B2 · 1 mark · Explains skaters move in opposite directions with equal and opposite momentum.
B3 · 1 mark · States total momentum remains zero after push (conserved).
Worked solution
Before pushing, both skaters are at rest so total momentum is zero. When they push off, they move in opposite directions with equal and opposite momenta. The total momentum after is still zero, as momentum is conserved (no external forces).