Is momentum a vector or a scalar? why

-- Momentum is a vector.

-- The definition of momentum is        (mass) · (velocity).

-- Velocity is a vector.  Momentum is in the same direction as velocity.

Julia would be observing a. static electricity was caused by her sweater rubbing against her shirt and transferring electrons. she didn't touch anything metal, so that would cancel out b.she most likely didn't rub her sweater against her hair either, so that cancels out c.she also didn't scoot across the carpet while trying to take her sweater off, that cancels out d.so that leaves a.a. is correct.

That depends on what kind of environ meant it is in  in space it has the same force that was applied when the velocity was gained