Final velocity of this hockey puck

In summary, the conversation discusses the calculation of the final velocity of a puck after being shot into an empty net in a hockey game. The conversation includes equations and a problem with rounding errors and incorrect direction of acceleration. The final velocity is found to be the same as the initial velocity due to small acceleration.
  • #1
Ace.
52
0

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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  • #2
Well, you did do something wrong, but it won't affect your answer that much.

What direction is the acceleration going in?
 
  • #3
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.
 
  • #4
I feel dumb, thanks.
 
  • #5
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.
 

What is the final velocity of this hockey puck?

The final velocity of a hockey puck is the speed and direction at which it is moving at the end of its trajectory.

How is the final velocity of a hockey puck determined?

The final velocity of a hockey puck is determined by its initial velocity, the acceleration it experiences, and the distance it travels.

What factors can affect the final velocity of a hockey puck?

The final velocity of a hockey puck can be affected by factors such as air resistance, friction from the surface it is sliding on, and external forces like the impact from a stick or other players.

Can the final velocity of a hockey puck be calculated?

Yes, the final velocity of a hockey puck can be calculated using the equations of motion, which take into account the initial velocity, acceleration, and distance traveled.

Why is knowing the final velocity of a hockey puck important?

Knowing the final velocity of a hockey puck is important for understanding the speed and direction at which the puck will travel, which is crucial for making strategic plays and predicting where the puck will end up.

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