Impulse and Momentum (finding net force)

[acra]

A 0.500-kg ball is dropped from rest at a point 1.20 m above the floor. The ball reboundes straight upward to a height of 0.700 m. What are the magnitude and direction of the impulse of the net force applied to the ball during the collision with the floor?

I have been trying to solve this various ways, I have tried using PE and KE, but I keep on coming up with 3.1305 instead of the 4.28 which I should be getting.

Any guidance would be greatly appreciated.

[Andrew Mason]

A 0.500-kg ball is dropped from rest at a point 1.20 m above the floor. The ball reboundes straight upward to a height of 0.700 m. What are the magnitude and direction of the impulse of the net force applied to the ball during the collision with the floor?

I have been trying to solve this various ways, I have tried using PE and KE, but I keep on coming up with 3.1305 instead of the 4.28 which I should be getting.

Any guidance would be greatly appreciated.You have to determine the ball's change in momentum. To do that you need to know its speed immediately before and immediately after the impact with the floor.

Can you determine these speeds from the two heights given?

AM