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# Calculate max stress in a rod watch

1. The question is:

'A steel rod 30m long holds 1.5kN weight at its lower end as shown in Fig Q7.
Diameter of the rod is 6mm. Calculate maximal stress (MPa) in the rod when
neglecting the weight of the rod. Required accuracy is 0.1 MPa.'

I used
stress=Force/Area
1500/2.83x10-5=53MPa

However this doesn't take in to account the length of the bar so I'm not sure if it's correct?
2. Moved to Physics.
3. (Original post by Sljmaster)
The question is:

'A steel rod 30m long holds 1.5kN weight at its lower end as shown in Fig Q7.
Diameter of the rod is 6mm. Calculate maximal stress (MPa) in the rod when
neglecting the weight of the rod. Required accuracy is 0.1 MPa.'

I used
stress=Force/Area
1500/2.83x10-5=53MPa

However this doesn't take in to account the length of the bar so I'm not sure if it's correct?
If you can neglect the weight of the rod it can be any length you like. Unless there is something in the diagram, the stress is the same everywhere which makes me wonder why the word maximal has been used. You have not quoted to the required accuracy.
4. (Original post by nerak99)
If you can neglect the weight of the rod it can be any length you like. Unless there is something in the diagram, the stress is the same everywhere which makes me wonder why the word maximal has been used. You have not quoted to the required accuracy.
That's what I thought but as they gave me length made me question it. These are just practise questions but yes the accuracy is also wrong.

Thank you

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