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# Impossible fucking question!!

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A student hits a hockey puck, giving it an initial velocity of 6.0 m/s. If the coefficient of kinetic friction between ice and puck is 0.100, how far will the puck slide before stopping? This is impossible because it only gives you merely two pieces of information! I swear to god, this is the sole reason why physics is terrible! This subject is just useless and it sucks!

Feb 22, 2021

#1
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mass = 0.25 kg

initial velocity = v_i = 6 m/s

coefficient of kinetic friction = mu_k = 0.1

final velocity = v_f = 0 m/s

distance = d = ?

There are three forces acting on the puck (friction, gravity, normal force) Gravity and normal force cancel each other out, so we can ignore that for now.

Friction acts in the -x direction.

F_n = mg = (0.25 kg)(9.8 m/s^2) = 2.45 N

F_f = (mu_k) * (F_n) = (0.1) * (2.45) = 0.245 N

F = ma    ==>    a = F/ m = (0.245 N) / (0.25 kg) = 0.98 m/s^2

Finally, we use kinematics.

0 = (6^2) + 2(0.98)d

d = 18.367 m

My physics is a bit rusty so this is the best I can come up with.

Feb 22, 2021
#2
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If the question only gives you two pieces of information, you can try using variables to sub for the other variables you'll need to solve for the question. Most likely, the variables will cancel out, leaving you with the answer.

Feb 22, 2021
#3
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people are saying the μmg = ma. Why the h**l is the ma there?? The force of friction doesn't fucking equal the net force!!

Guest Feb 22, 2021
#4
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I haven't gotten up to that part in my physics classes yet, but you should try using variables to sub for the values you don't know.

Right now, what you have is this:

initial velocity: 6.0 m/s

final velocity: 0 m/s

Coefficiant of kinetic friction: 0.100

Draw a force diagram. Since it looks like you have more information on velocities, you might be able to find acceleration or something like that, use a few variables and more equations, and solve for the answer.

kagesuki  Feb 22, 2021
edited by kagesuki  Feb 22, 2021
#5
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If You Have Any Issue With Certain Math Problems Try To Use https://www.mathway.com

Guest Feb 22, 2021
#6
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Mathway is a pretty great website, but it's not for all types of problems.

kagesuki  Feb 22, 2021
#11
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We understand you are stressed, but could you please refrain from profanity. We want to keep this sight as calm and kind as possible! EP has kindly posted an answer with an explanation to your problem. Hope you have a great day!

~MathSolver4Lyfe

Guest Feb 24, 2021
#7
+31281
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Force of friction =   coefficient of friction * NORMAL force      Normal force = m a     = mass * 9.81 m/s^2

were you not given the mass of the hockey puck?

Feb 22, 2021
#8
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With the given parameters, the mass of the hockey puck is NOT required to solve this problem.

However, intelligence slightly above that of a hockey puck IS required to solve this problem.

It’s great to have you back, EP. You are my favorite member to troll.

GA

Feb 22, 2021
#9
+31281
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Thanx Troller !      Yah....I did not look very far in to this problem....I suspected 'm' may cancel out in there, but my pucked brain doesn't have time right now...... water pipes are leaking ......grrrrr!

~EP

ElectricPavlov  Feb 23, 2021
#10
+31281
+2

x = x0 + v0t + 1/2 at^2

f friction  = u m g                       (using g to avoid confusion)

ff = ma    and   = umg

a = u g

vf = vo + at

0 = 6  + u g t

0 = 6 - .1 (9.81) t       t = 6.12 sec

x = x0 + vo t - 1/2 at^2

=  0   + 6(6.12) - 1/2 (.1)(9.81)(6.12)^2  = 18.35    meters

NOW ---- off to fix those leaks.......

Feb 23, 2021