Question

8, 9, 10 .Explicați-mi să înțeleg și eu cum se rezolva.

Answer 1

$\displaystyle Componenta \ greutatii \ care \ tine \ corpul \ pe \ plan \ are \ valoarea: \\ \\ G_t=mgsin\alpha \\ \\ Forta \ de \ frecare \ are \ valoarea: \\ \\ F_f=G_n\mu=mg\mu cos\alpha \\ \\ Conditile \ de \ echilibru \ sunt: \\ \\ \vec{F}+\vec{F_f}+\vec{G_t}=0 \\ \\ \vec{N}+\vec{G_n}=0 \\ \\ F=G_t+F_f \\ \\ F=mgsin\alpha+mg\mu cos\alpha=mg(sin\alpha+\mu cos\alpha)\approx 17N \\ \\ \\ \\ L=Fh=200J \\ \\ \\ \\ F=ma\implies a=\frac{F}{m}=0,5m/s^2 \\ \\ a=\frac{v}{t}\implies v=at=1m/s \\ \\ E_c=\frac{mv^2}{2}=0,5J$

Answer 2

[tex]8)Se~da:\\ \\ m=2kg\\ \\ \alpha=45^\circ\\ \\ \mu=0,2\\ \\ F=?N\\ \\ \\ Formule:\\ \\ F=G_t+F_{fr}\\ \\[/tex]

[tex]F=G\times\sin\alpha+\mu\times N\\ \\ F=m\times g\times\sin\alpha+\mu\times G_n\\ \\ F=m\times g\times\sin\alpha+\mu\times G\times\cos\alpha\\ \\ F=m\times g\times\sin\alpha+\mu\times m\times g\times\cos\alpha\\ \\ F=m\times g\times(\sin\alpha+\mu\times\cos\alpha)\\ \\ \\ Calcule:\\ \\ F=2\times 10\times(\sin45+0,2\times\cos45)\approx 16,97N[/tex]


[tex]9)Se~da:\\ \\ F=20N\\ \\ h=10m\\ \\ L=?J\\ \\ \\ Formule:\\ \\ L=F\times h\\ \\ \\ Calcule:\\ \\ L=20\times 10=200J\\ \\ \\ Raspuns:~B)[/tex]



[tex]10)Se~da:\\ \\ F=0,5N\\ \\ m=1kg\\ \\ t=2s\\ \\ E_c=?J\\ \\ \\[/tex]


[tex]Formule:\\ \\ E_c=\frac{m\times v^2}2\\ \\ \\ v=a\times t\\ \\ \\ F=m\times a\\ \\ a=\frac Fm\Rightarrow v=\frac{F\times t}m\Rightarrow E_c=\frac{F^2\times t^2}{2\times m}\\ \\ \\ Calcule:\\ \\ E_c=\frac{0,5^2\times 2^2}{2\times 1}=0,5J[/tex]