Problem 7.39 Part A You are watching a hockey game on your digital video recorde
ID: 1772729 • Letter: P
Question
Problem 7.39 Part A You are watching a hockey game on your digital video recorder. Your team's goalie is at rest when he catches a 0.18-kg puck moving straight toward him. The announcer says it was a 50 m/s slap shot, based on radar gun data. Normally the goalie would be braced, but in this case he is resting on parallel skate blades so that there is negligible friction to impede his subsequent motion. The collision is too fast to observe quantitatively but by running the video in slow motion, you can tell that the goalie s glove is 150 mm from his body when the puck strikes and is right against his chest after the suessful catch. It is also clear that the stunned goalie (holding the puck) drifts backward at 71 mm/s for a second or two after the collision is over, The direction of the puckos initial velocity is the +x direction Compute the average acceleration of the puck during the collision Express your answer with the appropriate units puck- aue Submit My Answers Give Up Part B Compute the average acceleration of the goalie during the collision Express your answer with the appropriate units LA agoalie = Value Submit My Answers Give UpExplanation / Answer
Solution:
a) Acceleration of the puck = a = (vf^2 - vi^2 ) / 2d
= (50^2 - 0^2 ) /2*0.150
= 8333 m/s/s = 8.3 x103 m/s2.
b) Time of impact = t = 50/(8333 ) = 0.006 s = 6 ms
During this short duration, goalie steps back at 71mm/s
a =vf-vi/t = 71-0/6 = 11.8 mm/s2 =0.012m/s2 .