The initial speed of the student would be 5.32 m/s.
The mass of the skateboard is determined by applying the principle of conservation of linear momentum.
[tex]m_1 u_1 + m_2 u_2 = v(m_1 + m_2)\\\\47.4(4.2) \ + m(0) = 3.95(47.4 + m)\\\\199.08 = 187.23 + 3.95 m\\\\11.85 = 3.95m\\\\m = \frac{11.85}{3.95} \\\\m = 3 \ kg[/tex]
The initial speed of the student is determined by applying the principle of conservation of linear momentum.
[tex]m_1 u_1 + m_2 u_2 = v(m_1 + m_2)\\\\47.4u_1 + 3(0) = 5(47.4 + 3)\\\\47.4u_1 + 0 = 252\\\\u_1= \frac{252}{47.4} \\\\u_1 = 5.32\ m/s[/tex]
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