Calculating Average Force on a Ball Hitting a Hard Surface

[takando12]

Homework Statement

A ball weighing 10g hit s ahard surface vertically with a speed of 5m/s and rebounds with the same speed.The ball remains in contact with the surface for 0.01 sec. The average force exerteed by the surface on the ball is :a) 100N b)10N c)1N d) 0.1N

Homework Equations

The Attempt at a Solution

using F= M(v₂-v₁)/t. I subs the values and converted g to kg.I also took the initial velocity as 5m/s and final as zero, time =0.01 sec . But I am getting 5 N. Where is my understanding flawed?

 

[haruspex]

rebounds with the same speed

final as zero

Compare those two statements.

 

[takando12]

oh...initial and final are same. 5-(-5)=10. Stupid me.Thank you sir.