I solved this problem from the homework correctly, but still got it wrong. I\'m
ID: 1314520 • Letter: I
Question
I solved this problem from the homework correctly, but still got it wrong. I'm wondering if anyone else had the same problem and if you can help me identify whether I did something wrong the I'm not noticing.
A baseball (m = 155 g) approaches a bat horizontally at a speed of 41.6 m/s (93.1 mi/h) and is hit straight back at a speed of 54.3 m/s (121 mi/h). If the ball is in contact with the bat for a time of 1.85 ms, what is the average force exerted on the ball by the bat? Neglect the weight of the bat, since it is so much less than the force of the bat. Choose the direction of the incoming ball as the positive direction.
1. I used the impulse momentum theorem.
?F = m(Vf - Vo) / ? t = .155kg (-54.3 m/s + 41.6 m/s) / 1.85 s = -8.03N
Because this is such a small magnitude of force, I'm guessing the error lies somewhere in decimal placement; however, this is all correct based on the numbers I was given in the homework problem.
Any suggestions?
Explanation / Answer
It appears to me that you are dividing by time in milliseconds instead of seconds.
As you have written
F=0.155kg*(41.5m/s-54.3m.s)/(0.00185 s) =-1072 Newtons
I hope this helps