Forces and moments -- Pushing wheeled luggage through the airport

[shk]

Homework Statement

This isn't my homework. I'm helping someone else with her homework. But I am not sure about part d.

Relevant Equations

F=ma

Hi
I need help with part d.
I think for part q(i) the force is horizontally and constant and equal to what I have found in part c. and for part d(ii) the force is upwards and equal to what I have found in part b.

 

[vanhees71]

Answering a known question can be difficult, but if the question is unknown, it's impossible!

 

[shk]

Answering a known question can be difficult, but if the question is unknown, it's impossible!

you are absolutely right. I have now attached the question. I thought I had done it.

 

[haruspex]

How do you have the man avoiding tilting the bag in your answer to c)?

 

[shk]

How do you have the man avoiding tilting the bag in your answer to c)?

He exerts a horizontal force to balance the moment of the weight. I know how to do that part by making the clockwise moment equal to anti clockwise moment.

 

[haruspex]

He exerts a horizontal force to balance the moment of the weight. I know how to do that part by making the clockwise moment equal to anti clockwise moment.

No, he was already balancing the moment of the weight by an upward force. How does he need to add a horizontal impulse to get the bag moving horizontally without making it tilt?
You are told to show the point of application. Where have you put that?
The answer is quite specific, and requires a little lateral thinking.

 

[shk]

No, he was already balancing the moment of the weight by an upward force. How does he need to add a horizontal impulse to get the bag moving horizontally without making it tilt?
You are told to show the point of application. Where have you put that?
The answer is quite specific, and requires a little lateral thinking.

Hi
Sorry I accidentally said horizontally.
I have now answered the question and have attached it for you to see. Please let me know if I've made a mistake .
Thanks

 

[haruspex]

Hi
Sorry I accidentally said horizontally.
I have now answered the question and have attached it for you to see. Please let me know if I've made a mistake .
Thanks

Well, maybe I am misreading the question.
It gives the impression that the force applied to get the case in motion is in addition to the upward force, if so, the answer would be that he pushes it with his foot at the height of its mass centre, something I have done myself.
Now I notice that it asks for the magnitude, which suggests that your interpretation is correct, but if so it should say he momentarily exerts a horizontal force instead, .. and why bother to ask where it is applied?
So I'm left uncertain as to which answer is expected.

For d) the foot is not an option, so it will be a change in force on the handle. It could be any combination of a horizontal pull and a vertical force that balances the torque of the case's weight.

 

[shk]

Well, maybe I am misreading the question.
It gives the impression that the force applied to get the case in motion is in addition to the upward force, if so, the answer would be that he pushes it with his foot at the height of its mass centre, something I have done myself.
Now I notice that it asks for the magnitude, which suggests that your interpretation is correct, but if so it should say he momentarily exerts a horizontal force instead, .. and why bother to ask where it is applied?
So I'm left uncertain as to which answer is expected.

For d) the foot is not an option, so it will be a change in force on the handle. It could be any combination of a horizontal pull and a vertical force that balances the torque of the case's weight.

I totally agree with you in terms of the missing word "instead ". This is where all my problem's coming from .
So is my answer correct if we assume that the horizontal force has been applied instead of the vertical force?

 

[haruspex]

I totally agree with you in terms of the missing word "instead ". This is where all my problem's coming from .
So is my answer correct if we assume that the horizontal force has been applied instead of the vertical force?

Yes.

 

[shk]

Yes.

Thank you very much. I appreciate the time you took to help me .