Question

rezolvati doar ce stiti
multumesc tare mult​

Answer 1

S1

1. Ec₁=mv₁²/2

Ec₂=mv₂²/2

Ec₁/Ec₂=mv₁²/2/mv₂²/2=v₁²/v₂²=4²/8²=16/64=1/4=>Ec₂=4Ec₁

a crescut de 4 ori

2.m=200 g=0,2 kg

m*v=2=>v=2/m=2/0,2=10 m/s

Ec=mv²/2=0,2*10²/2=0,1*100=10 J

3.F₁=(F₀+F₀₁)/2=

F₀=0

F₀₁=-kΔl/3

F₁=-kΔl/3/2=-kΔl/6

L₁=-F₁*Δl/3=-(-kΔl/6)*Δl/3=kΔl²/18

F₂=(F₀₂+F)/2

F₀₂=-k*2Δl/3

F=-kΔl

F₂=(-k*2Δl/3-kΔl)/2=-5kΔl/6

L₂=-F₂*Δl/3=-(-5kΔl/6)*Δl/3=5kΔl²/18

L₁/L₂=kΔl²/18/5kΔl²/18=1/5

4.m₁=fm

m₂=(1-f)m

G₁=m₁g=fmg

G₁-Ff=0=>G₁=Ff

N₂-G₂=0=>N₂=G₂=m₂g=(1-f)mg

Ff=μN₂=μ(1-f)mg

G₁=Ff=>fmg=μ(1-f)mg |:mg=>f=μ(1-f)<=>f=μ-μf<=>f(1+μ)=μ=>f=μ/(1+μ)=0,25/(0,25+1)=0,25/1,25=0,2

x₀=(1-f)l=(1-0,2)*20=0,8*20=16 cm

5.N₂-mgcosβ=0=>N₂=mgcosβ=0,5*10*cos30°=5*0,866=4,33 N

N₁-mgcosα=0=>N₁=mgcosα=0,5*10*cos60°=5*0,5=2,5 N

N₁=2,5 N

N₂=4,33 N

S2.

b) Tr=Fel<=>Tr=kΔl=>Δl=Tr/k=2/200=0,01 m=1 cm

c) Vectorial:F+G+N+Ff=ma

Ox:Fx-Ff=ma<=>Fcosα-Ff=ma

Oy:N+Fy-mg=0<=>N+Fsinα-mg=0=>N=mg-Fsinα

Ff=μN=μmg-μFsinα

Fcosα-μmg+μFsinα=ma=>a=(Fcosα-μmg+μFsinα)/m=(3√2*√2/2-0,25*1*10+0,25*3√2*√2/2)/1=3-2,5+0,75=0,5+0,75=1,25 m/s²

d) Vectorial:G+N+Ff=ma'

Ox:-Ff=ma'

Oy:N'-mg=0=>N'=mg

Ff'=μN'=μmg

-μmg=ma'=>a'=-μg=-0,25*10=-2,5 m/s²

vf=v+a't<=>0=6-2,5t=>t=6/2,5=2,4 s