Help Solve Physics Homework: Computer Base Unit of Mass

[SherlockIsReal]

Hi! Another Physics homework question that needs solving immediately! Thank you in advance.

A computer base unit of mass 7.5 kg is dragged along a smooth desk. If the normal contact force is 23 N and the tension in the arm of the person dragging it acts at 23° to the horizontal, then what is the total tension in the persons arm?

 

[Andrew Mason]

It seems to me that you have left out a material fact. You will need to tell us what the co-efficient of kinetic friction is.

AM

 

[SherlockIsReal]

It seems to me that you have left out a material fact. You will need to tell us what the co-efficient of kinetic friction is.

AM

There can't be a coefficient of kinetic friction if there is no friction right, and there is no friction because it is smooth desk, right?

 

[Andrew Mason]

Being smooth does not necessarily imply a 0 coefficient of friction. Roads can be smooth too, but they have friction. But in looking at it again, it appears here that the question expects you to assume that it is negligible.

What does the fact that the normal force is 23N tell you?

AM

 

[SherlockIsReal]

Being smooth does not necessarily imply a 0 coefficient of friction. Roads can be smooth too, but they have friction. But it appears here that the question expects you to assume that it is negligible.

What does the fact that the normal force is 23N tell you?

AM

I think I got it. Would it make sense to solve it this way?
∑ Forces in y direction = Force Normal - Force gravity + Force tension in y direction

 

[Andrew Mason]

I think I got it. Would it make sense to solve it this way?
∑ Forces in y direction = Force Normal - Force gravity + Force tension in y direction

Yes. That would be right.

AM