need help in mechanics - forces, question 9c
- Thread starter azif345
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D
Deleted member 4993
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The first thing you must do in these problems to draw combined and individual dynamic diagram (indicating acceleration/deceleration) and FBD (showing forces acting on the body). Have you done that?
D
Deleted member 4993
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Assuming x-axis positive to the right:
what are the forces that are being applied to the car+ trailer (include direction)?
what are the forces that are being applied to the car (include direction)?
what are the forces that are being applied to the trailer (include direction)?
D
Deleted member 4993
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Did your instructor make-up this problem or is it from a text-book (which book)?
The reason I am asking that is that the statements in the problem are strangely worded. A car equipped with engine - can only accelerate/decelerate due to friction. Nevertheless, please explain your FBD (you should have at least two FBDs - one while the system is accelerating due to "engine thrust" and next one while the system is decelerating. Which way the car is accelerating, initially?
Remember, that the tow bar creates internal force - so when you draw the system (car+carriage) FBD, the thrust (force) in the tow-bar will not be "visible" in the FBD.
All the external forces drawn in your FBD is pointed to right (+x direction) - that is incorrect. Draw correct FBD including indication of +x direction.
Why do you have a = 0?
However, part (a) of the question asks you to prove that the initial acceleration of the system is = 0.75 m/s2
Do that next - (after drawing correct FBD of the system and before trying calculate forces while decelerating).