(hrw8c9p40) A space vehicle is traveling at 4350 km/h relative to the Earth when the exhausted rocket motor is disengaged and sent backward with a speed of 64 km/h relative to the command module. The mass of the motor is four times the mass of the module. What is the speed (km/h) of the command module relative to Earth after the separation?

Respuesta :

Answer:4298.8 km/h

Explanation:

Given

velocity of space vehicle [tex]v_i=4350\ km/h[/tex]

Mass of motor is 4 times the mass of module

suppose m is the mass of module therefore

mass of motor is 4 m

velocity of disengaged motor is 64 km/h   relative to command module

we can write

[tex]v_{me}=v_{mc}+v_{ce}[/tex]

where [tex]v_{me}[/tex]=velocity of motor relative to earth

[tex]v_{mc}[/tex]=velocity of motor relative to command module

[tex]v_{ce}[/tex]=velocity of command relative to earth

Conserving momentum

[tex]M(v_i)=4m(v_{me})+mv_{ce}[/tex]

where M is combined mass of motor and module

[tex]Mv_i=4m(v_{mc}+v_{ce})+mv_{ce}[/tex]

[tex]5mv_i=4mv_{mc}+4mv_{ce}+mv_{ce}[/tex]

[tex]5mv_i=4mv_{mc}+5mv_{ce}[/tex]

[tex]v_{ce}=v_i-\frac{4}{5}\times v_{mc}[/tex]

[tex]v_{ce}=4350-\frac{4}{5}\times 64[/tex]

[tex]v_{ce}=4350-51.2[/tex]

[tex]v_{ce}=4298.8\ km/h[/tex]

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