Suppose the total mass of a chair and its occupant is 161 kg. a.)Calculate the t

Question

Suppose the total mass of a chair and its occupant is 161 kg.

a.)Calculate the tension in the cable attached to the chair.A 2.32 kg block is held in equilibrium on an incline of angle q = 65.7o by a horizontal force, F.

b.) If the coefficient of static friction between block and incline is ms = 0.256, determine the minimum value of F.

I got 28.45 N for the tension of the cable by doing (2.32*9.81)[(sin(65.7))-(.256cos(65.7))]/(cos(65.7)+.256sin(65.7)). Which is correct.

However, for part b, I did R=F*Sin(65.7)+[(2)*(9.81)*(cos(65.7))] and got 34.003 N which is apparently wrong. What am I doing wrong?

Explanation / Answer

a) T - mg = ma

since a= 0 m/s^2

T= mg = 161*9.8 = 1577.8 N

b)

Fnet = F – Fs - mgsin= ma = 0

F = Fs + mgsin = us*Fn + mgsin = us* mgcos + mgsin = 0.256*2.32*9.8*cos65.7 + 2.32*9.8*sin65.7 = 23.11 N

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