Leroy, who has a mass of 100 kg, is skateboarding at 9.0 m/s when he smacks into a brick wall and comes to a dead sop in 0.2 s.

 

Answer

A) Deceleration = inital speed - final speed / total time taken so ... 9-0/.2 = 9/.2= 45m/s^2 B) Force= (mass)(velocity) / (time) so..... (9)(100) / .2 = 900/.2 = 4500 N Source