The following position-dependent net force acts on a 3 kg block:

[F subscript n e t end subscript open parentheses x close parentheses equals open parentheses 3 straight N over straight m squared close parentheses x squared]If the block starts at rest at x = 2 m, what is the magnitude of its linear momentum (in kgm/s) at x = 4 m?

Respuesta :

Answer:

Explanation:

Given

F_net(x)  = (3 x²) N

m v dv / dt = 3 x²

m v dv = 3 x² dx

integrating on both sides and taking limit from x = 2 to 4 m

m v² / 2 - 0 = 3 x³ / 3

mv² / 2 = 4³ - 2³

mv² / 2 = 64 -  8

3 x v² /2 = 56

v = 6.11 m / s

linear momentum

= m v

= 3 x 6.11

= 18.33 kgm/s

Answer:

[tex]p=m.v=37\ kg.m.s^{-1}[/tex]

Explanation:

Given:

  • [tex]F_{net}=3x^2\ [N][/tex]
  • The initial position of the block, [tex]x=2\ m[/tex]
  • mass of the block, [tex]m=3\ kg[/tex]
  • final position of the block, [tex]x=4\ m[/tex]

WE know from the Newton's second law:

[tex]\frac{d}{dt} (p)=F[/tex]

where:

[tex]p=[/tex] momentum

[tex]F=[/tex] force

[tex]t=[/tex] times

Now put the values

[tex]\frac{d}{dt} (mv)=3\cdot x^2[/tex]

[tex]m.\frac{d}{dt} (v)=4\times x^2[/tex]

Now integrate both sides from final limit to initial:

[tex]m.v=\int\limits^4_2 {3x^2} \, dx[/tex]

[tex]m.v=[\frac{3x^3}{3} ]^4_2[/tex]

[tex]m.v=4^3-2^3[/tex]

[tex]p=m.v=56\ kg.m.s^{-1}[/tex]