1. A 0.0048kg pullet traveling with a speed of 200m/s penetrates a large wooden fence post. If the average resisting force exerted on the bullet was 4500N how far did the bullet penetrate. 2. F=ma? 3. F = ma F/m = a 4500/0.0048 = 937500? So there's a reverse acceleration of 937500m/s? 200/937500 = 0.000213 So it takes 0.000213 seconds for the bullet to stop and it has an average speed of 100m/s. Therefore the bullet travels 0.0213m or 2.13cm. Well that's my wrong answer, according to the book it's 8.5cm. Where did I go wrong, I'm sorry I'm very clueless.