Torques in equilibrium w/ angle

AI Thread Summary
To balance a meter stick with a pivot at 1/4 its length, the force required when pulling upward at a 30-degree angle to the vertical can be calculated using torque equilibrium. The discussion emphasizes the importance of identifying the center of mass and its distance from the pivot point to determine the gravitational torque. The torque from the string must counterbalance this gravitational torque, with careful attention to the sine and cosine components of the angle. The equilibrium condition is established by setting the sum of torques to zero, leading to the equation T1 + T2 = 0. Understanding these principles is crucial for accurately predicting the necessary force to maintain equilibrium.
supercherrie
Messages
1
Reaction score
0
on a meter stick the pivot point is placed at 1/4 its length; predict the force needed to balance the meter stick by pulling upward on the end of it with a string making an angle of 30 degrees w/ respect to the vertical.

Me trying to solve it:
sigma T=0
T1+T2=0
T1 = 0 <--this is the pivot point, i think it equals 0 b/c we what to reach equilibrium
T2 = rFsin(theta)
0+rFsin(theta)
F=-0/(rsin(theta)) ?
 
Physics news on Phys.org
supercherrie said:
T1+T2=0
T1 = 0 <--this is the pivot point, i think it equals 0 b/c we what to reach equilibrium
It's the '=0' in 'T1+T2=0' that says we're to reach equilibrium. T1 is the torque from the gravitational force. Where is the centre of mass of the stick? How far from the pivot point? What torque does it exert?
As for the string, it's 30 degrees to the vertical. Be careful about sine versus cosine. (As a check, I always think to myself, what if the specified angle were zero? Would the force be zero or max?)
 
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