Răspuns: A) desenul il faci deja singur.
B)h=60 cm=0,6 m
sinα=h/l=0,6/2,5=0,25
D²=l²-h²=2,5²-0,6²=6,25-0,36=5,89=>D=±√5,89=±2,42 m
D>0=>D=2,42 m
cosα=D/l=2,42/2,5=0,97
F-Gt-Ff=0<=>F-mgsinα-Ff=0
N-Gt=0=>N=mgcosα
Ff=μN=μmgcosα
F-mgsinα-μmgcosα=0=>F=mg(sinα+μcosα)=50*10(0,25+0,5*0,97)=500*0,73=365 N
C) Lu=mgh=0,6*10*50=300 J
D)L=F*l=365*2,5=912,5 J
E) ctgα=cosα/sinα=0,97/0,25=3,88
η=1/(1+μctgα)=1/(1+0,25*3,88)=1/1,97=0,5
