- #1

teoferrazzi

- 18

- 0

## Homework Statement

So you have this dumbbell, that is lying on a two-dimensional xy plane, and is made of two masses - m1 and m2, with m2 to the ''right'' on the x-axis [the text doesn't specify, but it's probably a good idea to place m1 in the origin]. suddenly you apply a force F in the negative y direction on m1 for dt. Calculate the rotation rate of the dumbbell.

## The Attempt at a Solution

an impulse Fdt causes a change in momentum mv. I presume the other mass m2 experiences the same change in momentum, so it will experience the same change in momentum; the change in linear velocity will be inversely proportional to the mass, but the angular velocity will be the same because the distance to the centre of mass is also inversely proportional to the mass. so the dumbbell will rotate uniformly [which is obvious]. the problem is that a hint given in the question says i should use conservation of several momenta. but this force is obviously external. how does that work with conservation? and does the whole impulse translate into angular velocity?