- #1
Fatima Hasan
- 319
- 14
Homework Statement
Homework Equations
W = ΔUg + ΔkE + ΔUs
KE = 0.5 m v^2
Ug = m g h
Us = 0.5 k x^2
The Attempt at a Solution
k = 60 N/m vi=0 m/s (" the block is released from rest ") xi= 0 m/s ( "the spring is unstreached") vf= 0 m/s xf= 0.2 * sin 37 = 0.2*0.6 = 0.12 m d= 0.2 m hf=0 hi= 0.2*sin37 = 0.12m m= 2 kg μκ = ?
W = Fκ d cos θ
Fk = FN μk
Fk = mg cos θ ( mg must be decompose)
Fk = 2*10*0.8 = 16 N
so , W = 16 * 0.2 * cos 180 * μκ = - 3.2 μκ
W = ΔUg + ΔkE + ΔUs
since the velocity is constant , ΔkE = 0 --> W = Δ Us + ΔUg
- 3.2 μκ = 0.5 k xf^2 - 0.5 * k xi^2 + mghf - mghi
- 3.2 μκ = 0.5 * 60 * ( 0 )^2 - 0.5*60*( 0.12 )^2 + 2*10*0 - 2*10*0.12
- 3.2 μκ = -0.432 - 2.4
- 3.2 μκ = -2.832
μκ = 0.885
This is my tried , but I don't know where is my mistake.
Any help would be greatly appreciated !