The 8 kg block is then released and accelerates to the right, toward the 2 kg block. The surface is rough and the coefficient of friction between each block and the surface is 0.4 . The two blocks collide, stick together, and move to the right. Remember that the spring is not attached to the 8 kg block. Find the speed of the 8 kg block just before it collides with the 2 kg block. Answer in units of m/s.

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Answer:

3.258 m/s

Explanation:

k = Spring constant = 263 N/m (Assumed, as it is not given)

x = Displacement of spring = 0.7 m (Assumed, as it is not given)

[tex]\mu[/tex] = Coefficient of friction = 0.4

Energy stored in spring is given by

[tex]U=\dfrac{1}{2}kx^2\\\Rightarrow U=\dfrac{1}{2}\times 263\times 0.7^2\\\Rightarrow U=64.435\ J[/tex]

As the energy in the system is conserved we have

[tex]\dfrac{1}{2}mv^2=U-\mu mgx\\\Rightarrow v=\sqrt{2\dfrac{U-\mu mgx}{m}}\\\Rightarrow v=\sqrt{2\dfrac{64.435-0.4\times 8\times 9.81\times 0.7}{8}}\\\Rightarrow v=3.258\ m/s[/tex]

The speed of the 8 kg block just before collision is 3.258 m/s

The speed of the 8kg block before collision on the given rough surface is 2.5 m/s.

The given parameters;

  • mass of the first block, m₁ = 8 kg
  • mass of the second block, m₂ = 2 kg
  • coefficient of friction, μ = 0.4

let the spring constant, K = 450 N

let the distance between the blocks, x = 0.5 m

The energy stored in the spring is calculated as follows;

[tex]U = \frac{1}{2} kx^2\\\\U = \frac{1}{2} \times 450 \times 0.5^2\\\\U = 56.25 \ J[/tex]

Apply the principle of conservation of linear momentum, to determine the speed of the 8kg block before collision.

[tex]\frac{1}{2} mv^2 = U - \mu F_n \\\\\frac{1}{2}\times 8 \times v^2 = 56.25 \ - \ 0.4 \times 8\times 9.8\\\\4v^2 = 24.89\\\\v^2 = \frac{24.89}{4} \\\\v^2 = 6.23\\\\v = \sqrt{6.23} \\\\v =2.5 \ m/s[/tex]

Thus, the speed of the 8kg block before collision on the given rough surface is 2.5 m/s.

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