1. The problem statement, all variables and given/known data A 0.5 kg object drops from rest from a 3m high point. On bouncing from Earth it rises to a height of 2m. The collision with Earth lasts for about 10^-4 seconds. i) What is the impulse received by the object? ii)Considering that there is a gravitational force present, Can you assume that in the collision F(ext)=0? If so, what is the change in the Earth's momentum? iii)Is this collision totally elastic? Justify. 2. Relevant equations J=F*(delta)t F=ma 3. The attempt at a solution i)So, I've got the first part down. Impulse will be the mass*acceleration*change in time. Which is (.5)(9.8)(10^-4) = 0.00049 This is where I need help: ii)I'm not sure if this can be assumed. If there IS a change in the earth's momentum and F(ext)=0, it would just be -0.00049... But I'm unsure about this part. Help? iii) If this was totally elastic, the ball would return to 3m high, not 2m - right? So this is NOT totally elastic. (Let me know if I'm confused here.) Thank you in advance for helping me to understand this.