How Do You Calculate Work and Force for a Displaced Mail Bag?

AI Thread Summary
To calculate the horizontal force needed to hold a displaced mail bag weighing 140 kg, the angle from the vertical is crucial, which is 22 degrees in this case. The correct tension in the rope should be recalculated, as the initial value of 1272 N was deemed incorrect. The horizontal force can be determined using the formula F = T * sin(θ), where T is the tension and θ is the angle. For work done, the formula W = F * d * cos(θ) applies, where d is the displacement. Accurate calculations will yield the correct answers for both the force and the work done.
melodrameric
Messages
7
Reaction score
0
Hi there, I'm new here, and I desperately need help with this work/energy business. Here's my problem:

A mail bag with a mass of 140 kg is suspended by a vertical rope of length 8.00 m.
a) What horizontal force is necessary to hold the bag in a position displaced sideways a distance 3.00 m from its initial position?
b) How much work is done by the worker in moving the bag to this position?

I know that the angle from the vertical will be 22 degrees, and that the tension in the rope will be 1272 N (or am I wrong?), but I don't know where to go from there.

By the way, this is for a Mastering Physics problem, and I've already found out that 476.5 N [1272*cos(68)]is a wrong answer.

Thank you!
 
Physics news on Phys.org
You got the tension wrong, that's all. It looks like your method is OK.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top