Force acting on steel rod (deformation)

[foo9008]

in this problem , i could only understand that P3 = 120KN , i can't understand why P2= -60kN and why P1 = 240kN ? can someone explain ?

Homework Equations

The Attempt at a Solution

 

[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 .

 

[foo9008]

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 .

What do you mean? can you explain further?

 

[Chestermiller]

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

 

[foo9008]

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

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

 

[Chestermiller]

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

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?

 

[foo9008]

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?

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

 

[Chestermiller]

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

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?

 

[foo9008]

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?

yes

 

[Chestermiller]

F = 300 -180 + 120