Imagine a rigid pole sticking up through the ice on a frozen pond. A skater glid
ID: 2034772 • Letter: I
Question
Imagine a rigid pole sticking up through the ice on a frozen pond. A skater glides rapidly toward the pole. Let her mass be m. What would be her angular momentum relative to the pole at the instant she is a distance d from the pole if she were skating directly toward it at speed v?
mvd
zero
impossible to determine
What would be her angular momentum relative to the pole at the instant she is a distance d from the pole if she were skating at speed v along a straight path that is a perpendicular distance a from the pole?
impossible to determinezero
mvd
mva
Explanation / Answer
1) If p and r are parallel or antiparallel, the angular momentum is zero. For a nonzero angular momentum, the linear momentum vector must be offset from the rotation axis. So (zero)
2) The angular momentum is the product of the linear momentum and the perpendicular distance from the rotation axis to the line along which the linear momentum vector lies. So mva