How Do You Calculate Final Velocity with Given Force and Time?

[KatieLynn]

Homework Statement

Find the final velocity of the object if it is initially moving along the x-axis with average velocity of -62 m/s.

Other information
mass=.462kg
time=5s
average force = 0.8N
impulse=4

Homework Equations

F=m(Vf-Vi)/t

The Attempt at a Solution

I use the equation like this

(0.8N)=(.426kg)(Vf+62m/s)/(5s)

=-61.13m/s Is that right?

 

[dvdqnoc]

I don't know why they gave you impulse, you can solve the problem with this equation:

Vf = Vi + at

where Vf=final velocity, Vi=initial velocity, a=acc. and t=time.

Remember - the acc. is .8/.462 because F=ma, so a=F/m.

Good luck!

 

[KatieLynn]

Vf = Vi + atVf= (-62m.s) + (.8/.462)(5)

= -53.3 m/s

Thats what I got but it isn't right. I'm sure I didn't up the algebra, did I plug something in wrong?

 

[dvdqnoc]

well then i guess your initial approach is correct. the equation I gave might not work because i didnt read the part that said "avg velocity". I think your -61 is correct