Can someone please answer this

Conservatives forces

What object a collides with object b and bounces back its final momentum is?

What does si stand for,when referring to a system of measurement

Aball thrown by ginger is moving upward through the air. diagram a shows a box with a downward arrow. diagram b shows a box with an upward arrow. diagram c shows a box with a downward and upward arrow equal in size. diagram d shows a box with a downward and upward arrow with the downward arrow larger in size. which force diagram represents the forces on the ball? you may neglect the effects of air resistance.