Question

VA ROG MULT!
1. 2 corpuri de mase-m1=1kg si m2=2kg
Aflate pe un plan orizontal fara frecari cu miu-0 si Ff.-0
Sunt legate intre ele printr-un fir. De corpul m2 se trage cu o forta orizontala F=12N
Calculati: accelaratia sistemului si Tensiunea din fir. Se considera acc. grav. g=10m/s2
calculati:N1,N2


2. Rezolvati aceiasi problema cu miu=0.1

Answer 1

1.

pt. m2: Vectorial: F+N2+G2+T=m2a

Scalar:Ox:F-T=m2a (1)

          Oy:N2-m2g=0=>N2=m2g=2*10=20 N

pt.m1:Vectorial:T+N1+G1=m1a

Scalar:Ox:T=m1a (2)

          Oy:N1-m1g=0=>N1=m1g=1*10=10 N

(1)+(2)=>F=(m1+m2)a=>a=F/(m1+m2)=12/3=4 m/s²

T=m1a=1*4=4N

2.

pt. m2: Vectorial: F+Ff2+N2+G2+T=m2a

Scalar:Ox:F-Ff2-T=m2a

          Oy:N2-m2g=0=>N2=m2g=2*10=20 N

Ff2=μN2=μm2g

F-μm2g-T=m2a (1)

pt.m1:Vectorial:T+N1+G1+Ff1=m1a

Scalar:Ox:T-Ff1=m1a

          Oy:N1-m1g=0=>N1=m1g=1*10=10 N

Ff=μN1=μm1g

T-μm1g=m2a (2)

(1)+(2)=>F-μ(m1+m2)g=a(m1+m2)=>a=F/(m1+m2)-μg=12/6-1=4-1=3 m/s²

T=m1(a+μg)=1(3+1)=1*4=4 N