## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

We first find the rate $R$ that the mass is used. $R = \frac{mass}{time}$ $R = \frac{250~kg}{30~s}$ $R = 8.33~kg/s$ We then find the exhaust speed $v_{ex}$ of the hot gases; $F_{thrust} = v_{ex}~R$ $v_{ex} = \frac{F_{thrust}}{R}$ $v_{ex} = \frac{15,000~N}{8.33~kg/s}$ $v_{ex} = 1800~m/s$ The exhaust speed of the hot gases is 1800 m/s.