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[Grade 12 Physics - Momentum] How can I calculate the force of friction in this scenario?
'A lunch box is sliding across the floor at 4.3 m/s. 1.3 s later, it is going 2.1 m/s
a) calculate the change in momentum
b) calculate the force of friction
c) calculate mu, the coefficent of friction.'
I've already found the change in momentum to be ~0.9 N/s, but I don't remember how to find friction and the coefficent of friction. Any assistance would be greatly appreciated. :)
1 Answer
- Some BodyLv 74 years agoFavorite Answer
What you didn't tell us was the mass. Assuming you got the right answer to part a, the mass is 0.41 kg.
a) Change in momentum
Δp = m₁ v₁ - m₂v₂
Δp = (0.41) (4.3) - (0.41) (2.1)
Δp = 0.90 Ns
b) Force of friction
Change in momentum = net force * time
Δp = F Δt
0.90 Ns = F (1.3 s)
F = 0.69 N
c) Coefficient of friction
Assuming this is a level floor:
F = Nμ = Wμ
μ = F/W
μ = (0.69 N) / (0.41 kg * 9.8 m/s²)
μ = 0.17
