Thread: physics help...

"A hockey puck on a frozen pond with an initial speed of 16.3 m/s stops after sliding a distance of 220.5 m. Calculate the average value of the coefficient of kinetic friction between the puck and ice."

-i thought i knew what to do, it seemed simple enough. i found the deceleration, speed divided by time (time=distance divided by speed). And then it should be deceleration divided by gravity?(f=uN) i get the wrong answer so obviously not. am i doing something wrong??

Once it starts sliding, the only force acting on the puck is friction so:
where is the normal force

So first find the deceleration of the puck: - You have the final velocity (it's stops!), the initial velocity, and its distance.

So after solving for , use the equation from the first line:

Originally Posted by sarabolha

"A hockey puck on a frozen pond with an initial speed of 16.3 m/s stops after sliding a distance of 220.5 m. Calculate the average value of the coefficient of kinetic friction between the puck and ice."

-i thought i knew what to do, it seemed simple enough. i found the deceleration, speed divided by time (time=distance divided by speed). And then it should be deceleration divided by gravity?(f=uN) i get the wrong answer so obviously not. am i doing something wrong??

You need to find

If you draw a free body diagram, you should get something like this:



To find acceleration, use the kinematic equation

Now let's do a FB analysis:

:

Thus,

:

Thus,

Therefore,

Does this make sense?

--Chris

ah that was too easy i'm embarrassed. but you explained it very very well, thanks!!