(13%) Problem 8: A young 46-kg ice hockey goalie\' originally at rest, catches a

Question

(13%) Problem 8: A young 46-kg ice hockey goalie' originally at rest, catches a 0.125-kg hockey puck slapped at him at a speed of 33 m/s. In this problem, take the original direction of the puck as positive × 50% Part (a) Suppose the goalie and the ice puck have an elastic collision and the puck is reflected back in the direction from which it came. What would the final velocity of the puck, in meters per second, be in this case? Grade Summary Deductions Potential 0c 100 sin0 cos) cotan0asin acos0 atan0 acotan sinhO cosh0 tanh cotanh0 O Degrees Radians tan Submissions Attempts remaining (090 per attempt) detailed view *123 0% 0% END NO Submit Hint I give up! Hints: for a deduction. Hints remaining: What quantities are conserved in such a collision? came. What would the final velocity, in meters per second, of the goalie be in this case? Feedback: 0% deduction per feedback. 50% Part (b) Suppose the goalie and the ice puck have an elastic collision and the puck is reflected back in the direction from which it

Explanation / Answer

A.

Using momentum conservation:

Pi = Pf

m1u1 + m2u2 = m1v1 + m2v2

u1 = initial velocity of puck = 33 m/sec

u2 = initial velocity of goalie = 0 m/sec

v1 = final velocity of puck = ?

v2 = final velocity of goalie = ?

m1 = 0.125 kg, m2 = 46 kg

0.125*33 + 46*0 = 0.125*v1 + 46*v2

Also we know that

v2 - v1 = u1 - u2

v2 - v1 = 33 - 0

v2 = v1 + 33

Using above relation

0.125*33 = 0.125*v1 + 46*(v1 + 33)

v1 = (0.125*33 - 46*33)/(0.125 + 46)

v1 = -32.82 m/sec

v2 = -32.82 + 33 = 0.18 m/sec

Part A, final speed of puck = -32.82 m/sec

Part B, final speed of goalie = 0.18 m/sec

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