Distance calculated from Energy

[azncocoluver]

Please help me with part b, thank you!

 

[Simon Bridge]

Complete the following so the sentences are true:

The particle starts with ________J kinetic energy.
Work done on the particle increases/decreases it's kinetic energy.

Now how is the Work related to the distance the particle travels?

To help you properly, really need to see your working.

 

[azncocoluver]

The particle starts with 0 J kinetic energy.

Force relates the work to the distance the particle travels.

 

[Simon Bridge]

The particle starts with 0 J kinetic energy.

Doesn't the particle have some initial velocity?

Select "increases" or "decreases" for the second sentence.

 

[azncocoluver]

Well, at x=0, the Force is 2 Newtons but the x is 0, so wouldn't 2N * 0m = 0 J?

Work done on the particle increases it's kinetic energy.

 

[Simon Bridge]

OK - you've forgotten about the initial velocity. When I read part (b) I see this:

(b) if it starts with a velocity of 2m/s in the +x direction, how far will the particle go in that direction before stopping?

Thus - how much kinetic energy is it starting with?

 

[azncocoluver]

Ooh okay, it's 1 J.

 

[Simon Bridge]

No worries - the eye sometimes skips part of a question. Hate it when that happens :)

 

[azncocoluver]

Thanks :] So once I have 1 J, how do I solve for the distance? I added 1 J to the 3 J at x = 4. W = fd so.. 4 J = F d. What would be my F?

 

[Simon Bridge]

You don't need F. Look at your graph. You did it correctly when you thought you started with 0J energy - do the same thing only starting with 1J

So - you start with 1J
In the first meter moved, you gain 1J (area under F-x graph) for a total of 2J
What happens in the next meter moved?
How far before you've lost all the KE?

 

[azncocoluver]

2.5m! Thanks so much, I really appreciate your help :)