Question

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?

Answer 1

Average acceleration is `-"1.2 ms"^-2` and coefficient of frictional force is `0.12`

Explanation:

Average deceleration `(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`