# Force acting on steel rod (deformation)

1. Jun 24, 2016

### foo9008

in this problem , i could only understand that P3 = 120KN , i cant understand why P2= -60kN and why P1 = 240kN ? can someone explain ?

2. Relevant equations

3. The attempt at a solution

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2. Jun 24, 2016

### Nidum

In the same way that you can do a shear force diagram for lateral loads on a beam you can do a tension force diagram for axial loads on a shaft .

Basically plot a graph of axial tension against position along shaft . Have a try .

3. Jun 24, 2016

### foo9008

What do you mean? can you explain further?

4. Jun 24, 2016

### Staff: Mentor

If you do a force balance on the entire rod, what do you get for the reaction force on the left end?

5. Jun 24, 2016

### foo9008

how to do it ? i know only the P3 .... which is 120kN , how to do for P1 and P2 ?

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6. Jun 24, 2016

### Staff: Mentor

You have 3 forces acting on the rod: 300 kN, 180 kN, and 120 kN. In order of the rod to be in static equilibrium, there must also be a force applied by the wall on the bar at location A. What does that force have to be?

7. Jun 24, 2016

### foo9008

what i found is this ? how to find the force applied by the wall on the bar at location A. ??
btw , i am not sure which 1 is P3 and which one is P2

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8. Jun 24, 2016

### Staff: Mentor

Forget about P1, P2, and P3 for now. Are you saying that you don't know how to do a 1 dimensional equilibrium force balance on a solid object?

9. Jun 24, 2016

### foo9008

yes

10. Jun 24, 2016

### Staff: Mentor

F = 300 -180 + 120

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