A 10 g bullet is fired into, and embeds itself in, a 2 kg block attached to a spring with a force constant of 19.6 n/m and whose mass is negligible. How far is the spring compressed if the bullet has a speed of 300 m/s just before it strikes the block and the block slides on a frictionless surface? Use conservation of momentum.

Respuesta :

Answer:

[tex]x=0.478\ m[/tex] is the compression in the spring

Explanation:

Given:

  • mass of the bullet, [tex]m=10\ g=0.01\ kg[/tex]
  • mass of block, [tex]M=2\ kg[/tex]
  • stiffness constant of the spring, [tex]k=19.6\ N.m^{-1}[/tex]
  • initial velocity of the spring just before it hits the block, [tex]u=300\ m.s^{-1}[/tex]

Now since the bullet-mass gets embed into the block, we apply the conservation of momentum as:

[tex]m.u=(M+m).v[/tex]

[tex]0.01\times 300=(2+0.01)\times v[/tex]

[tex]v=1.4925\ m.s^{-1}[/tex]

Now this kinetic energy of the combined mass gets converted into potential energy of the spring.

[tex]\rm Kinetic\ energy=Spring\ potential\ energy[/tex]

[tex]\frac{1}{2} (M+m).v^2=\frac{1}{2} k.x^2[/tex]

[tex]\frac{1}{2} \times (2+0.01)\times 1.4925^2=\frac{1}{2} \times 19.6\times x^2[/tex]

[tex]x=0.478\ m[/tex] is the compression in the spring

Answer: 19.5

Explanation: