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Object is accelerated from rest , find KE

  • Thread starter discosucks
  • Start date
  • #1
23
3

Homework Statement



An object is accelerated from rest by a force of 32 N over a distance of 18 m. Calculate the
kinetic energy of the object after 18 m

Homework Equations



KE = 0.5 • m • v^2[/B]

The Attempt at a Solution



I cant work out where ill be able to get the mass or the velocity for this one?
 

Answers and Replies

  • #2
Doc Al
Mentor
44,892
1,143
I cant work out where ill be able to get the mass or the velocity for this one?
Hint: Maybe you won't need those quantities. Any other principles you know that have to do with energy?
 
  • #3
105
3
I cant work out where ill be able to get the mass or the velocity for this one?
You can work them out if you wish , if we can put 'a' in term of 'm' [From the given force] , we can find the final velocity using the equations of motion with constant acceleration [the acceleration is constant because the force is constant] .

But this method is quite long .However, as Mr @Doc Al said, there is a shorter method that has to do with work and energy , could you figure it out?

:)
 
  • #4
23
3
ummm

well the force by the distance will give me the work done

32 x 18 = 576J

Im almost sure there is a relationship between work and KE but i cant work out what ?:)
 
  • #5
105
3
ummm

well the force by the distance will give me the work done

32 x 18 = 576J

Im almost sure there is a relationship between work and KE but i cant work out what ?:)
Well, have you studied Work-Kinetic energy theorem ?
 
  • #6
23
3
Yes but im not sure i totally understand what to do when with the formula we have

2ufq5jp.png
 
  • #7
Doc Al
Mentor
44,892
1,143
That's the formula you need! What does it say? (In words.)
 
  • #8
23
3
If im totally honest Im not sure what KEf and KEo stand for .
 
  • #9
105
3
If im totally honest Im not sure what KEf and KEo stand for .
Work-Kinetic energy says :
"For a particle , a change in the kinetic energy equals the net work done on the particle "

In the formula you give :

KEf stands for final kinetic energy of the object.
KE0 stands for initial kinetic energy of the object.
 
  • #10
105
3
I Hope you get the point now ,,.
 
  • #11
23
3
Ah so the work done is the same as the KE !

I know the work done is 576J so thats the same as the KE!

thanks for your help :)
 
  • #12
105
3
The work done is equal to the value of KEf - KE0 But KE0 is zero since the object has started from the rest [the velocity is zero] so the final kinetic energy is equal to the work done by the object..


:)
 
  • #13
23
3
Oh perfect i actually over looked that! thaks again for your help!
 

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