Answer:
[tex]1863.9\ \text{kg}[/tex]
Explanation:
[tex]m_1[/tex] = Mass of car = 1571 kg
[tex]u_1[/tex] = Initial velocity of car = 129 km/h
[tex]u_2[/tex] = Initial velocity of the animal = 0
[tex]v[/tex] = Velocity of combined mass = 59 km/h
[tex]m_2[/tex] = Mass of the animal
As the momentum of the system is conserved we have
[tex]m_1u_1+m_2u_2=(m_1+m_2)v\\\Rightarrow \dfrac{m_1u_1+m_2u_2}{v}-m_1=m_2\\\Rightarrow m_2=\dfrac{1571\times 129+0}{59}-1571\\\Rightarrow m_2=1863.9\ \text{kg}[/tex]
The mass of the animal is [tex]1863.9\ \text{kg}[/tex].