2. The FBD you choose depends on what forces you want to find

3. The FBD you choose depends on what forces you want to find
If you want to know the force in this hydraulic
Piston, then…

4. The FBD you choose depends on what forces you want to find
If you want to know the force in this hydraulic
Piston, then…
The FBD would “cut” the Hydraulic Piston so
That the force on the piston is EXTERNAL to
The FBD

5. The FBD you choose depends on what forces you want to find

6. The FBD you choose depends on what forces you want to find
If the driver is pulling on the steering wheel and
You want to analyze the forces on the driver, then…

7. The FBD you choose depends on what forces you want to find
If the driver is pulling on the steering wheel and
You want to analyze the forces on the driver, then…
This might be the FBD

8. The FBD you choose depends on what forces you want to find
If the driver is pulling on the steering wheel and
You want to analyze the forces on the driver, then…
Wheel pulls on
The driver
This might be the FBD

9. The FBD you choose depends on what forces you want to find
If the driver is pulling on the steering wheel and
You want to analyze the forces on the driver, then…
Floor pushes
Back on the
Driver
This might be the FBD

10. The FBD you choose depends on what forces you want to find
If the driver is pulling on the steering wheel and
You want to analyze the forces on the driver, then…
His weight
Goes down
This might be the FBD

11. The FBD you choose depends on what forces you want to find
If the driver is pulling on the steering wheel and
You want to analyze the forces on the driver, then…
The seat pushes
Back up
This might be the FBD

12. What FBD do we choose to find the wheel reaction forces at H and K?

13. What FBD do we choose to find the wheel reaction forces at H and K?

14. What FBD do we choose to find the wheel reaction forces at H and K?
The seat pushes
Back up

15. What FBD do we choose to find the wheel reaction forces at H and K?
The seat pushes
Back up

16. What FBD do we choose to find the wheel reaction forces at H and K?
For the GIVEN Problem,
these are internal forces, not external
FBD
The seat pushes
Back up