"total energy ":E_k=1/2*m*v^2" (at A)"total energy :Ek=12⋅m⋅v2 (at A)
"energy changed heat due to friction :" W_f=mu* m*g*cos (pi/3)*lenergy changed heat due to friction :Wf=μ⋅m⋅g⋅cos(π3)⋅l
"potential energy for the point of A :"E_p=m*g*hpotential energy for the point of A :Ep=m⋅g⋅h
"we can write the energy conservation equation as :"we can write the energy conservation equation as :
E_k=E_p+W_fEk=Ep+Wf
1/2*m*v^2=m*g*h+mu*m*g*cos (pi/3)*l12⋅m⋅v2=m⋅g⋅h+μ⋅m⋅g⋅cos(π3)⋅l
"so ;"h=l.sin (pi/3)so ;h=l.sin(π3)
1/2*cancel(m)*v^2=cancel(m)*g*l*sin(pi/3)+mu*cancel(m)*g*cos (pi/3)*l
1/2*v^2=g*l*0,87+1/3*g*0,5*l
v^2=g*l(2*0,87+(2*0,5)/3)
v=7 m/s
7^2=g*l(1,74+1/3)
49=g*l((5,22+1)/3)
49=g*l*2,07
g=9,81 m/s^2
49=9,81*l*2,07
49=20,31*l
l=2,41 " meters"