# The Naked Scientists Forum

### Author Topic: How is work calculated?  (Read 2523 times)

#### Cathy Erwin

• Guest
##### How is work calculated?
« on: 20/11/2011 22:30:02 »
Cathy Erwin  asked the Naked Scientists:

Hi,

My son in grade 9 has just asked me to help him with an exam question, for his Physical Science exam, which is TOMORROW!!!

A 75kg man pushes against a 500 000 ton wall for 250 seconds. The wall does not move. How much work is done?

He says the equation is Work = force x distance

If distance is 0 then surely the answer is 0?

Thanks and kind regards,

Cathy

What do you think?
« Last Edit: 20/11/2011 22:30:02 by _system »

#### Soul Surfer

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• keep banging the rocks together
##### How is work calculated?
« Reply #1 on: 20/11/2011 23:04:07 »
One should not help with homework or exam questions but what you have expressed seems to show a correct understanding of the situation

#### yor_on

• Naked Science Forum GOD!
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• (Ah, yes:) *a table is always good to hide under*
##### How is work calculated?
« Reply #2 on: 20/11/2011 23:11:16 »
Show him this one and see what he thinks
What are "energy" and "work".

#### syhprum

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##### How is work calculated?
« Reply #3 on: 21/11/2011 05:12:26 »
Although in the strictly technical sense no work is done the man infact is dissipating energy in his muscles generating the force that he applies to the wall.
I think after 250 seconds he will have worked up quite a sweat

#### simplified

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##### How is work calculated?
« Reply #4 on: 21/11/2011 16:53:45 »
There is no time of moving of the wall.

#### Geezer

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• "Vive la résistance!"
##### How is work calculated?
« Reply #5 on: 21/11/2011 18:45:45 »
There is no time of moving of the wall.

Unless you want to be powerful, it doesn't matter how much time you take to do your work

#### Bored chemist

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##### How is work calculated?
« Reply #6 on: 21/11/2011 21:31:36 »
Cathy Erwin  asked the Naked Scientists:

Hi,

My son in grade 9 has just asked me to help him with an exam question, for his Physical Science exam, which is TOMORROW!!!

A 75kg man pushes against a 500 000 ton wall for 250 seconds. The wall does not move. How much work is done?

He says the equation is Work = force x distance

If distance is 0 then surely the answer is 0?

Thanks and kind regards,

Cathy

What do you think?

I think you should be pleased that he understands physics better than you .

#### The Naked Scientists Forum

##### How is work calculated?
« Reply #6 on: 21/11/2011 21:31:36 »