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

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 :)