A 0.0125 kg bullet strikes a 0.240 kg block attached to a fixed horizontal spring whose spring constant is 2.25*10^3N/m and sets it into oscillation with amplitude of 12.4 cm. What was the initial speed of the bullet if the two objects move together after impact?

Respuesta :

Answer:

The  value is  [tex]u_1 =  236 \ m/s[/tex]

Explanation:

From the question we are told that

   The  mass of bullet  is  [tex]m_b  =  0.0125 \  kg[/tex]

   The  mass of the block is  [tex]M_B  =  0.240 \  kg[/tex]

    The  spring constant is  [tex]k  =  2.25*10^{3} \  N/m[/tex]

   The  amplitude is  [tex]A= 12.4 \ cm  =  0.124 \ m[/tex]

Generally according to the conservation of momentum is  

     [tex]m_b u_1 + M_B  u_2 =  (m_b + M_B) v[/tex]

given that the block was at rest we have that

        [tex]m_b u_1  =  (m_b + M_B) v[/tex]

Now the angular velocity of the both bodies is mathematically represented as

     [tex]w =  \sqrt{\frac{k}{M_B  + m_b} }[/tex]

          [tex]w = \sqrt{\frac{ 2.25*10^{3}}{ 0.0125 + 0.240 } }[/tex]

         [tex]w =  94.4 \  rad/s[/tex]

Given that the system after collision set into oscillation

The maximum  linear velocity of the system after impact  is mathematically represented as

       [tex]v  = A * w[/tex]

      [tex]v  =  94.4 *0.124[/tex]

      [tex]v  =  11.7 \  m/s[/tex]

From above equation

    [tex]u_1  =  \frac{(m_b +  M_B ) * v}{m_b}[/tex]

=>    [tex]u_1 =  \frac{(0.240 + 0.0125) *  11.7}{ 0.0125}[/tex]

=>   [tex]u_1 =  236 \ m/s[/tex]