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

AI Thread Summary
To calculate the final velocity of an object with an initial average velocity of -62 m/s, a mass of 0.462 kg, and an average force of 0.8 N applied over 5 seconds, the impulse-momentum theorem can be applied. The equation F = m(Vf - Vi)/t can be rearranged to find Vf, leading to a calculation of approximately -61.13 m/s. However, using the alternative equation Vf = Vi + at, where acceleration a is derived from a = F/m, yields a different result of -53.3 m/s. The discussion highlights confusion regarding the use of impulse and the correct application of equations to find final velocity. Ultimately, the initial calculation of -61.13 m/s is deemed correct by some participants in the discussion.
KatieLynn
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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?
 
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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!
 
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?
 
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
 
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