Object is accelerated from rest , find KE

[discosucks]

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 can't work out where ill be able to get the mass or the velocity for this one?

 

[Doc Al]

I can't 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?

 

[Maged Saeed]

I can't 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?

:)

 

[discosucks]

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 can't work out what

 

[Maged Saeed]

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 can't work out what

Well, have you studied Work-Kinetic energy theorem ?

 

[discosucks]

Yes but I am not sure i totally understand what to do when with the formula we have

 

[Doc Al]

That's the formula you need! What does it say? (In words.)

 

[discosucks]

If I am totally honest I am not sure what KEf and KEo stand for .

 

[Maged Saeed]

If I am totally honest I am 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 :

KE_f stands for final kinetic energy of the object.
KE₀ stands for initial kinetic energy of the object.

 

[Maged Saeed]

I Hope you get the point now ,,.

 

[discosucks]

Ah so the work done is the same as the KE !

I know the work done is 576J so that's the same as the KE!

thanks for your help :)

 

[Maged Saeed]

The work done is equal to the value of KE_f - 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..:)

 

[discosucks]

Oh perfect i actually over looked that! thaks again for your help!