A hockey puck is hit on a frozen lake and starts moving with a speed of 12.0 m/s. Exactly 5.0 s later, its speed is 6.0 m/s. What is the puck’s average acceleration, and what is the coefficient of kinetic friction between puck and ice?

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Answer 1 · 2018-08-11T14:54:58

Average acceleration is $- {1.2 ms}^{- 2}$ $-"1.2 ms"^-2$ and coefficient of frictional force is $0.12$ $0.12$

Average deceleration $(a_{v})$ $(a_v)$ is equal to change in velocity in given time.

So, $a_v =((12-6) \ "ms"^(-1))/"5 s" = 6/5 \ "ms"^-2$

Now, if this happened due to frictional force then we can say that the frictional force acting was

$f=muN=mumg$

where $mu$ is coefficient of frictional force and $m$ is its mass.

So, the deceleration caused by the force is

$f/m=mug$

And this is equal to $a_v$ . So,

$a_v=mug$

Putting $g=9.8ms^-2$ , we get

$mu=a/g=(6/5) \ "ms"^(-2)xx(1/(9.8 \ "ms"^(-2)))=0.12$