Question

A spacecraft engine ejects mass at a rate of $30\text{kg/s}$ with an exhaust velocity of $3000\text{m/s}$. What is the thrust of the engine in vaccum?

• A. $90,000\text{N}$
• B. $9000\text{N}$
• C. $900000\text{N}$
• D. $900\text{N}$

Answer 1

The correct option is A $90,000\text{N}$

Given, rate of ejection of mass$\frac{dm}{dt}=\mu =30\text{kg/s}$
and exhaust velocity
$V_r=3000\text{m/s}$
As we know,
$F_{thrust}=V_r\left|\frac{dm}{dt}\right|$
$F_{thrust}=3000\times 30$
$F_{thrust}=90,000\text{N}$