Question

cine face priblemele de la 26-28
primeşte coroană, de tote

Answer 1

26.

Vectorial:F+N+G+Ff=0

Ox:Fcosα-Ff=0=>Ff=Fcosα

Oy:N+Fsinα-mg=0=>N=mg-Fsinα

Ff=N/2<=>2Fcosα=mg-Fsinα<=>G=2Fcosα+Fsinα=2*10*0,866+10/2=22,32 N

27.

L1=40 cm=0,4 m

L2=20 cm=0,2 m

m1=100 g=0,1 kg

m2=300 g=0,3 kg

Fel1=G1=m1g=0,1*10=1 N

Fel2=G2=m2g=0,3*10=3 N

Fel1=k(Lo-L1)

Fel2=k(-Lo+L2)

____________":"

Fel1/Fel2=(L1-Lo)/(Lo-L2)<=>1/3=(-Lo+0,4)/(Lo-0,2)<=>-3Lo+1,2=Lo-0,2<=>-4Lo=-1,4=>Lo=0,35 m=35 cm

Δl1=L1-Lo=40-35=5 cm

Δl2=Lo-L2=35-20=15 cm

Fel1=kΔl1=>k=Fel1/Δl1=1/0,05=20 N/m

28.

Vectorial:Fel+G+N+Ff=0

Scalar:Ox:Felsinα-Ff=0=>Ff=Felsinα

Oy:Felcosα+N=mg=>N=mg-Felcosα

Ff=μN=μ(mg-Felcosα)

Fel=kΔl=k(l-lo)

cosα=lo/l=>l=lo/cosα=>Fel=klo(1-cosα)/cosα=10*0,1(1-0,5)/0,5=2*0,5=1 N

l=lo/cosα=0,1/0,5=0,2 m

Δl=l-lo=0,2-0,1=0,1 m

N=mg-Felcosα=0,5*10-1/0,5=5-2=3 N

Ff=Felsinα=1*√3/2=1*0,866=0,866 N

Ff=μN=>μ=Ff/N=0,866/3=0,288