# Physics

posted by
**Tammy**
.

A rocket whish is in deep space and initially at rest relative to an inertial reference frame, has a mass of 2.55 X 10^5 kg of which 1.81 X10^5 kg is fuel. The rocket engine is then fired for 250 s during which feul is consumed at the rate of 480 kg/s. The speed of the exhaust products relative toe the rock is 3.27 km/s. a) what is the rocketâ€™s thrust? B) After the 250s firing what is the mass c) the speed of the rocket after the 250s firing?

a) I would multiply 1.81x10^5*480

b) Would I used the answer from a) and divide by acceleration?

c)i am not sure what to do for this part

Thrust=mv/t= m/t *v You are given the fuel burn rate (m/t) and v.

massleft= intial mass - fuelburnrate*time

Speed of rocket= thrust*timeburn/avgmassrocket

where average mass of rocket= starting mass -fuelburned/2