A Heavy Meterstick Has Mass M

Multiple Choice

A heavy meterstick has mass m. When the meterstick is thrown like a spear past you at speed v, you measure its momentum to be 2mv. What do you measure its length to be?

A) 1 m
B) 0.87 m
C) 0.5 m
D) 0.25 m
E) none of the above