Rocket Momentum: Max Velocity Calculation

[tani]

Homework Statement

Far in space, where gravity is negligible, a 495 kg rocket traveling at 85.0 m/s fires its engines. The impulse imparted to the rocket is 15000Ns, for 30 seconds. What is the maximum velocity of the rocket?

Homework Equations

F(delta t)=mv2-mv1

The Attempt at a Solution

v2=((15000*30)+(495*85))/495
v2=994m/s
Why isn't this answer correct?

 

[PhanthomJay]

Homework Statement

Far in space, where gravity is negligible, a 495 kg rocket traveling at 85.0 m/s fires its engines. The impulse imparted to the rocket is 15000Ns, for 30 seconds. What is the maximum velocity of the rocket?

Homework Equations

F(delta t)=mv2-mv1

The Attempt at a Solution

v2=((15000*30)+(495*85))/495
v2=994m/s
Why isn't this answer correct?

The impulse is given as 15000 Newton-seconds. you have incorrectly used this value as a force of 15000 Newtons.

 

[D H]

Force has units of Newtons, not Newton-seconds. The impulse, 15000Ns, is not a force. The time duration has already been factored in.