[SOLVED] Average Retarding Force Problem 1. The problem statement, all variables and given/known data An arrow of mass 45 g strikes a wood block target horizontally with a velocity of 70 ms-1 and penetrates a distance of 280 mm. Ignoring air resistance, calculate (a) the time it takes for the arrow to stop moving, and (b) the average retarding force exerted on the arrow by the wood block target. 2. Relevant equations v=u + at F= ma V2=u + 2as 3. The attempt at a solution I worked out the time using the 1st formula listed (t=7.14 3sf) but when i go to work out the average retarding force using F=ma and get 0.44145 which seems wrong to me .Could someone please tell where i'm going wrong? I also worked out the total distance travelled by the arrow which is 250m including the 280mm penetration of the wood.