Mechanical energy. questions

[pete94857]

Homework Statement

Is a continuous applied force of 2.5kg over a distance of 5mm in a lateral motion equal to or more than 2.5w of mechanical energy ?

Relevant Equations

1w=1Nm=0.981kgm

1 watt equals 1 Newton metre

1 kg equals 9.81 Newton metres

2.5 kg = 24.525 Nm = 24.525 Watts of mechanical energy.

 

[PhDeezNutz]

This question is messed up to me, Watts are a unit of power, not energy. Are you sure you don't mean Joules?

Let me correct your units/conversions

1 Joule (J) = 1 Newton Meter (Nm)
1 watt (W) = 1 Joule/second (J/s)

also kg is a unit of mass not force.

If I were to make a correction to your question statement it would be

"Does a 2.5 Newton force applied over a distance of 5mm result in 2.5 J or more of work done?"

 

[pete94857]

I see, thank you.

But if 1kg is equal to 9.81 Nm what it not be , is 9.81Nm equal to 2.5 J or more ?

 

[Aurelius120]

I see, thank you.

But if 1kg is equal to 9.81 Nm what it not be , is 9.81Nm equal to 2.5 J or more ?

$1kgf$ (=1 kilogram force) is equal to $9.81$ Newtons and is a unit of weight $$1kgf=1kg\times g=1kg\times 9.81ms^{-2}=9.81N$$
$\text{ g is acceleration due to gravity}$

Also $1watt=1Nms^{-1}$

 

[pete94857]

I'm assuming this is in a vertical movement with a reference to gravity. Therefore is applying the force laterally parallel with gravity I'm assuming the ×9.81 m/s would be cancelled out. ?

What I'm actually trying to answer is for example , if I had a coil beside a permanent magnet, the coil was connected to a cord the coil moves laterally horizontal to gravity, the cord then goes round a single pully wheel with a 2.5kg weight attached to it. It is allowed to fall 5mm , would this be enough to produce 12 v assuming the magnet and coil are optimum. Also assuming no drag or friction ?

How would I work this out ?

 

[jbriggs444]

I'm assuming this is in a vertical movement with a reference to gravity. Therefore is applying the force laterally parallel with gravity I'm assuming the ×9.81 m/s would be cancelled out. ?

This is very confusing. "laterally parallel with gravity" means both horizontal and vertical. It does not clarify anything. The 9.81 that you probably mean is the acceleration of gravity. That is 9.81 m/s/s. Not 9.81 m/s.

What I'm actually trying to answer is for example , if I had a coil beside a permanent magnet, the coil was connected to a cord the coil moves laterally horizontal to gravity, the cord then goes round a single pully wheel with a 2.5kg weight attached to it. It is allowed to fall 5mm , would this be enough to produce 12 v assuming the magnet and coil are optimum. Also assuming no drag or friction ?

12 Volts is a voltage. It has dimensions of energy per unit charge. For example, joules per coulomb.

If the 2.5 kg weight falls 5 mm, that releases an amount of energy. But we cannot know how many volts correspond to that energy unless we know how much charge has been moved.

Start with the simple stuff: How much energy is released when a 2.5 kg weight falls 5 mm vertically under gravity with a strength of 9.81 m/s² ?

 

[kuruman]

What I'm actually trying to answer is for example , if I had a coil beside a permanent magnet, the coil was connected to a cord the coil moves laterally horizontal to gravity, the cord then goes round a single pully wheel with a 2.5kg weight attached to it.

Your description brings the picture below to my mind. The string is pulling laterally on the coil. Pretend that the magnet is fixed on the table and "beside" instead of "inside" the coil. Am I close?

Are the ends of the coil connected to anything?

 

[berkeman]

Thread closed temporarily for Moderation...

 

[berkeman]

Unfortunately, via private communication I've discovered that the OP is working on an Over-Unity mechanism, which we do not discuss here at PF. @pete94857 -- Please read the links below to help you understand why what you are trying to do will not work.

Pseudoscience, such as (but not limited to):
Perpetual motion and "free energy" discussions (see our Insights Article here)
http://en.wikipedia.org/wiki/Perpetual_motion
http://www.skepdic.com/freeenergy.html
http://www.skepdic.com/perpetual.html

https://www.physicsforums.com/insights/why-we-dont-discuss-perpetual-motion-machines-pmm/

 

[Nugatory]

It is allowed to fall 5mm , would this be enough to produce 12 v assuming the magnet and coil are optimum. Also assuming no drag or friction ?

Depending on the details of your coil and magnet it could produce 12v or 12000v or any other voltage you want. However, a higher voltage means that either less current will flow or or the current will flow for a shorter time. The total amount of charge moved by the current, times the voltage, will be equal to the energy derived from lowering the mass.