Fred (60 kg) is rollerblading at a velocity of 25 km/h [E] when he sees a broken glass bottle on the path ahead. He brakes and is slowed to a velocity of 8 km/h [E] in 4.2 s. What is the coefficient of friction between Fred's rollerblades and the ground? (Hint: Find FN and Ff first.)(adsbygoogle = window.adsbygoogle || []).push({});

Given:

m = 60 kg

v1 = 25km/h = 6.94m/s [E]

v2 = 8km/h = 2.20m/s [E]

Δt = 4.2s

g = 9.8 N/kg

Required:

?

Solution:

Fg = mg

Fg = (60kg) (9.8 N/kg)

Fg = 588 N

FN = Fg

FN = 588 N

Ff ≤ µs FN

Ff ≤ µs (588 N)

???????

I don't know what to do after.

µs is not given, so how do you solve this question?

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