How do you work out the coefficient of friction without the mass????

I've never come across a question where you need to do this before, and we haven't been taught it, so I'd appreciate some help if anyone knows how... just to clarify, I'm not after the answer, but rather the method that I should use, so I can apply it to similar questions...

We're told that an ice hockey puck is hit at 30 m/s. it travels 50 m in 1.68 s. Find the coefficient of friction between the puck and ice.

Thanks in advance :biggrin:

Call the mass m and see what happens?

Original post by TeslaCoil

I've never come across a question where you need to do this before, and we haven't been taught it

By the way please do not expect to have been taught or have seen every single variant of every question. The point is you are supposed to be developing a battery of skills you can apply to tackle ANY question you are faced with no matter how unfamiliar it may seem.

Reply 3

TeslaCoil

OP

Original post by Mr M

Call the mass m and see what happens?

Yes, I tried this, but then got confused when I ended up with a negative answer... Also, I'm aware that I shouldn't expect to be familiar with every question, I just thought that maybe there was another equation of which I was unaware...

Reply 4

james22

16

You know initial speed, distance and time so the first thing you should be thinking is equations of motion.

Reply 5

james22

16

Original post by TeslaCoil

Yes, I tried this, but then got confused when I ended up with a negative answer... Also, I'm aware that I shouldn't expect to be familiar with every question, I just thought that maybe there was another equation of which I was unaware...

Post your working.

Reply 6

TeslaCoil

OP

Original post by james22

You know initial speed, distance and time so the first thing you should be thinking is equations of motion.

ok, so this is what i did, it's just that my answer is negative, and i don't think that's right:

s 50
u 30
v
a ?
t 1.68

s = ut + 0.5 at^2
50 = 30 x 1.68 + 0.5 x a x 1.68^2
50 = 50.4 + 1.4112a
-0.4 = 1.4112a
a = -0.28345

F = ma
F = (mu)R

-0.28345m = (mu) x mg
-0.28345 = 9.8 (mu)
mu = -0.0289

Original post by TeslaCoil

Yes, I tried this, but then got confused when I ended up with a negative answer... Also, I'm aware that I shouldn't expect to be familiar with every question, I just thought that maybe there was another equation of which I was unaware...

You've probably just made a mistake with a sign. Remember friction OPPOSES motion.

How do you work out the coefficient of friction without the mass????

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you