What is the tension in the cable

[physicszman]

4) A rescue helicopter is lifting a man (weight- 822 N) from a capsized boat by the means of a cable and harness. (a) What is the tension in the cable when the man is given an initial upward acceleration of 1.10m/s^2? (b) What is the tension during the remainder of the rescue when he is pulled upward at constant velocity?

a) The mass of the man is 83.9kg

T = (83.9Kg)(9.80m/s^2+1.10m/s^2)

T = 914.5N

b) It is 822N because the velocity is constant.


5) Three forces act on a moving object. One force has a magnitude of 80.0N and is directed due norht. Another has a magnitude of 60.0N and is directed due west. What must be the magnitude and direction of the third force, such as the object continues to move with constant velocity.

I know how to find the magnitude, but have trouble finding the direction. Someone suggested tan(angle)= x/y. But when I do it out out i get a small number that couldn't possibly be the angle.

Thanks

 

[Doc Al]

You did problem 4 OK.

Originally posted by physicszman

I know how to find the magnitude, but have trouble finding the direction. Someone suggested tan(angle)= x/y. But when I do it out out i get a small number that couldn't possibly be the angle.

Show what you did. (You must have made an error somewhere!)

 

[physicszman]

Hi, thanks for your help.

I think I realized what I did wrong. You have to turn the formula around to solve for just the angle so its

angle = (80N/60N)/tan = 57.2

Do I answer the direction is 57.2 degrees North West?

 

[physicszman]

angle = (80N/60N)/tan = 57.2

Thats how I got the previous answer. How do I calculate it the right way?

And I guess it would be from the X axis since the y-component of the force is greater.

 

[physicszman]

Last question..

So what do I do with the 4/3 take the "arctan" of it?

Thanks

 

[physicszman]

53.1 degrees from west axis. I hope this sounds right. Thanks again for all your help!