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An average-sized asteroid located 5.0 x 10^7 km from Earth with mass 2.0 x 10^13 kg is detected headed directly toward Earth with speed of 2.0 km/s.
1. What will its speed be just before it hits the surface of the Earth? Assume the thickness of the atmosphere to be zero. (Ignore the size of the asteroid.) [average radius of Earth = 6.3781 x 10^6 m, mass of Earth = 5.972 x 10^24 kg]

Respuesta :

Answer:

[tex]v_f = 11.35 km/s[/tex]

Explanation:

Given data:

Earth mass [tex]= 5.972 \times 10^{24} kg[/tex]

distance between earth and asteroid is [tex]5.0\times 10^7 km[/tex]

asteroid mass [tex]= 2 \times 10^{13} kg[/tex]

speed of asteroid = 2 km/s

potential energy is [tex]U = - \frac{GM_e m}{R}[/tex]

[tex]U =- \frac{ 6.67 \times 10^{-11} \times 5.972 \times 10^{24} 2 \times 10^{13}}{5.0 \times 10^{10}}[/tex]

[tex]U = -0.0159 \times 10^{19} J[/tex]

Kinetic energy [tex]= \frac{1}{2} mv^2 = \frac{1}{2} \times 2\times 10^{13} \times (2\times 10^3)^2 = 4 \times 10^[19} J[/tex]

Final potential energy of asteroid is

[tex]U_f = potential energy is U = - \frac{GM_e m}{R}[/tex]

[tex]=- \frac{ 6.67 \times 10^{-11} \times 5.972 \times 10^{24} 2 \times 10^{13}}{6.371 \times 10^6}[/tex]

[tex]U_f = -125\times 10^{19} J[/tex]

from conservation of energy principle

[tex]U + K = U_f + K_f[/tex]

solving for K_f

[tex]K_f = U +K - U_F[/tex]

[tex]k_f = Kinetic energy = \frac{1}{2} mv_f^2[/tex]

[tex]v_f = \sqrt{\frac{2(U +K - U_F)}{m}}[/tex]

[tex]v_f = \sqrt{\frac{2\times (-0.0159 + 4+125) \times 10^{19}}{2\times 10^{13}}[/tex]

[tex]v_f = 11.35 km/s[/tex]