Answer:
the initial speed of the arrow before joining the block is 89.85 m/s
Explanation:
Given;
mass of the arrow, m₁ = 49 g = 0.049 kg
mass of block, m₂ = 1.45 kg
height reached by the arrow and the block, h = 0.44 m
The gravitational potential energy of the block and arrow system;
P.E = mgh
P.E = (1.45 + 0.049) x 9.8 x 0.44
P.E = 6.464 J
The final velocity of the system after collision is calculated as;
K.E = ¹/₂mv²
6.464 = ¹/₂(1.45 + 0.049)v²
6.464 = 0.7495v²
v² = 6.464 / 0.7495
v² = 8.6244
v = √8.6244
v = 2.937 m/s
Apply principle of conservation of linear momentum to determine the initial speed of the arrow;
[tex]P_{initial} = P_{final}\\\\mv_{arrow} + mv_{block} = (m_1 + m_2)V\\\\0.049(v) + 1.45(0) = (0.049 + 1.45)2.937\\\\0.049v = 4.4026\\\\v = \frac{4.4026}{0.049} \\\\v = 89.85 \ m/s[/tex]
Therefore, the initial speed of the arrow before joining the block is 89.85 m/s
The arrow moving as the speed of "76.36 m/s".
According to the question,
By using the conservation of energy, we have
→ [tex]K.E=P.E[/tex]
→ [tex]\frac{1}{2} (m_1+m_2)v_2^2= (m_1+m_2)gh[/tex]
or,
→ [tex]v_2 = \sqrt{2mgh}[/tex]
By substituting the values, we have
→ [tex]= \sqrt{2\times 9.8\times 0.44}[/tex]
→ [tex]=2.469 \ m/s[/tex]
Now,
By using the conservation of momentum, we get
→ [tex]m_1 v_1 = (m_1+m_2) v_2[/tex]
or,
→ [tex]v_1 = \frac{(m_1+m_2)v_2}{m_1}[/tex]
[tex]= \frac{1.45+0.049}{0.049}\times 2.469[/tex]
[tex]= 30.6\times 2.496[/tex]
[tex]= 76.36 \ m/s[/tex]
Thus the above approach is correct.
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