Inclined plane with massless, frictionless winch

AI Thread Summary
A 100 kg box is being pulled up a 45° inclined plane by a massless, frictionless winch with a constant angular velocity of 3.14 radians/sec. The coefficient of friction between the box and the plane is 0.25, and the winch completes 10 revolutions. The work done on the box is calculated using the formula W = mgh + uNd, where mgh represents gravitational potential energy gained and uNd accounts for frictional work. The correct answer for the work done is believed to be 13620 J, but the calculations need to accurately reflect the forces at play. Understanding the opposing forces and their impact on the distance moved is crucial for solving this problem correctly.
r34racer01
Messages
62
Reaction score
0
phys.jpg


A 100 kg box is pulled up an inclined plane by a massless, frictionless winch to which it is attached by a massless rope. The plane makes an angle of 45° with respect to the horizontal. The coefficient of friction between the box and the plane is μ = 0.25 (with μs = μk). The winch has a radius of 0.25 m and is turned at a constant angular velocity of ω = 3.14 radians/sec.

How much work is done on the 100 kg box by the rope when the winch makes 10 complete revolutions?

(a) 4380 J
(b) 5235 J
(c) 9262 J
(d) 12531 J
(e) 13620 J


So I did d = [2(.25)(3.34)]10 since we need 10 rev. And then...
W = mgh + uNd
W = mg(d sin 45) + u(mg cos 45)d
but I'm not getting the right answer, I think I'm suppose to get 13620J, but how do I get that?



 
Physics news on Phys.org
I'm not so sure that W = mgh + uNd
Isn't mgh the gravitational potential that is gained by doing the work?

I would sum up the forces that are opposing the pull of the rope (parallel to the plane) and multiply it by the distance it moves
 
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 'Collision of a bullet on a rod-string system: query'
In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
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