Final velocity of this hockey puck

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SUMMARY

The final velocity of a hockey puck, initially traveling at 41.5 m/s and subjected to a kinetic friction coefficient (μK) of 0.005, is calculated to be approximately 41.5 m/s. The puck's mass is 0.17 kg, and the normal force (FN) is determined to be 1.67 N. The frictional force (FK) was incorrectly calculated, leading to negligible acceleration (0.049 m/s²) that did not significantly alter the puck's speed. The primary errors identified were in the calculation of friction force and the direction of acceleration in the kinematic equations.

PREREQUISITES
  • Understanding of Newton's Second Law (F = ma)
  • Familiarity with kinematic equations (v² = v₁² + 2ad)
  • Knowledge of friction coefficients (μK)
  • Basic algebra for solving equations
NEXT STEPS
  • Review the calculation of friction force in physics problems
  • Study the effects of acceleration direction in kinematic equations
  • Learn about significant figures and their importance in scientific calculations
  • Explore real-world applications of Newton's laws in sports physics
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Students studying physics, particularly those focusing on mechanics and kinematics, as well as educators looking for examples of common errors in problem-solving.

Ace.
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Homework Statement



In the last second of a hockey game, a player slaps the puck in the empty net 32.5 m away. The puck leaves the stick with the speed of 41.5 m/s. Calculate the final velocity of the puck if its mass is 0.17 kg.

Homework Equations



μK = 0.005
μK = FK / FN
F = ma
v22 = v12 + 2ad

The Attempt at a Solution

Force normal of puck:
FN = Fg = m x g
= 0.17 kg x 9.8 m/s2
= 1.67 N​
μK = FK / FN
FK = μK / FN
= 0.005 / 1.67 N​
= 0.00835 N​

a = (Funbalance/ m)
= (0.00835 N / 0.17 kg​
)
0.049 m/s2

Finally, I solve for v2:
v2 = √(v12 + 2ad)
= √(41.52 + 2(0.049)(32.5)​
= 41.5 m/s2
My problem is that my final velocity is the same as my initial velocity? Where did I go wrong?
 
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Well, you did do something wrong, but it won't affect your answer that much.

What direction is the acceleration going in?
 
You went wrong twice: first, your algebra error when calculating friction force, which should be uk(N). Then , watch your signage for acceleration when using the kinematic equations.
 
I feel dumb, thanks.
 
You have two problems.
The acceleration is so small that you have lost the change in velocity in the rounding error. On the other hand, if you show more digits in your answer then you will be guilty of gaining precision: you'll have more significant digits in the answer than in the provided data. So the short answer is the change in speed is negligible.
Your second problem is that you have acceleration going the wrong way. The dynamic friction seems to be making your puck go faster.
 

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