# Final velocity, three forces, time, mass and velocity given

• want2learn
Add up the changes in v for each time interval to find the final velocity.In summary, a small robotic spacecraft with a mass of 145kg is initially moving in the +x-direction at 0.150 m/s. Its x-axis thruster exerts a force of -5.00 N during 0s<t<1.5s, -9.00 N during 1.5s<t<3.25s, and -6.00 N during 3.25s<t<4.00s. When the thruster stops firing at t=4.00s, the spacecraft's final velocity can be found by using F= ma to find the acceleration and then v= v0+ at

## Homework Statement

A small robotic spacecraft (m= 145kg) is initially moving in the +x-direction at .150 m/s. Then, its x-axis thruster exerts the following force on the spacecraft :
Fx(t) = -5.00 N during 0s<t<1.5s
-9.00 N during 1.5s< t< 3.25s
-6.00 N during 3.25s <t< 4.00s
When the thruster stops firing at t=4.00s, what is the spacecraft 's final velocity?

v= mt2

## The Attempt at a Solution

well...don't you have to find the displacement/"?

Well, you can find the deceleration of eachtime interval with Newton's second law, then go from there.

want2learn said:

## Homework Statement

A small robotic spacecraft (m= 145kg) is initially moving in the +x-direction at .150 m/s. Then, its x-axis thruster exerts the following force on the spacecraft :
Fx(t) = -5.00 N during 0s<t<1.5s
-9.00 N during 1.5s< t< 3.25s
-6.00 N during 3.25s <t< 4.00s
When the thruster stops firing at t=4.00s, what is the spacecraft 's final velocity?

## Homework Equations

v= mt2
What? where did you get this? It doesn't even have the right units: v is m/sec and mt^2 (which I guess you mean) is in kg sec^2. I think you meant F= ma. And then v= v0+ at.

## The Attempt at a Solution

well...don't you have to find the displacement/"?
No, you don't. It is not asked for and you don't need it to find the velocity, Use F= ma to find a and then use v= v0+ at to find t at the end of each time interval. v0 is the speed at the beginning of each time interval.