Answer:
Part a)
[tex]v_E = 2.5 \times 10^3 m/s[/tex]
Part b)
[tex]\frac{dm}{dt} = 52 kg/s[/tex]
Explanation:
Part a)
As we know that the velocity of exhaust with respect to the rocket is given as
[tex]v_{ER} = v_E - v_R[/tex]
so we will have
[tex]-5 \times 10^3 = v_E - 7.5 \times 10^3[/tex]
[tex]v_E = 2.5 \times 10^3 m/s[/tex]
Part b)
As we know that
[tex]F = ma[/tex]
here F = thrust force on the rocket
So we have
[tex]v_{ER} \frac{dm}{dt} = ma[/tex]
[tex](5 \times 10^3) \frac{dm}{dt} = (6.5 \times 10^4)(4)[/tex]
[tex]\frac{dm}{dt} = 52 kg/s[/tex]