Solving Static Forces/Torque Homework Problem

  • Thread starter khemist
  • Start date
  • Tags
    Static
In summary, the problem involves two sticks connected with hinges to a wall, with the bottom stick being horizontal and having a length L. The sticks form an angle of θ with each other. The goal is to find the horizontal and vertical components of the force that the wall exerts on the top hinge, and to show that the magnitude of the force goes to infinity for both θ → 0 and θ → π/2. The FBD shows that the wall and two sticks form a right triangle, with stick 1 having forces at the top hinge and bottom hinge, and stick 2 having a normal force and force of mg. The sum of forces for each stick is written down, but it is unclear if the forces
  • #1
khemist
248
0

Homework Statement



Two sticks are connected, with hinges, to each other and to a wall. The
bottom stick is horizontal and has length L, and the sticks make an angle
of θ with each other, as shown in Fig. 2.38. If both sticks have the same
mass per unit length, ρ, find the horizontal and vertical components
of the force that the wall exerts on the top hinge, and show that the
magnitude goes to infinity for both θ → 0 and θ → π/2

Homework Equations



F=ma
T=RF

The Attempt at a Solution



I drew my FBD as follows. The wall and two sticks form a right triangle. Stick 1 (at the angle) has mg pointing down, a force at the top hinge at some angle (F1x, F1y), and a force at the bottom hinge (F2x, F2y), where the two sticks meet, again at some angle. The bottom stick (horizontal, stick 2) has the normal force from the wall (N), pointing parallel to the stick, and the force of mg pointing down.

I attempted to write down the sum of the forces for each stick. For stick 1,
Fx = F1x + F2x = 0
Fy = F1y + F2y = 0

Stick 2:
Fx = N = 0
Fy = mg + F2x

To find the torque, I picked the hinge where the two sticks meet as my rotation origin, and my positive rotation is in the counter clockwise direction.
[tex] T = \frac{cos\phi}{L}(\frac{L}{2}m_{2}g + sin\phi m_{1}g\frac{L}{2cos\phi} - F_{1}(\frac{L}{cos\phi})) [/tex]

This is as far as I have gotten. I am pretty sure that my forces are not labeled correctly. Can anyone point me in the right direction? Thanks!
 
Physics news on Phys.org
  • #2
Where's the diagram?
 

1. How do I determine the net torque on an object?

To determine the net torque on an object, you must first identify all of the forces acting on the object and their respective distances from the axis of rotation. Then, calculate the torque of each force by multiplying its magnitude by its distance from the axis. Finally, add all of the torques together to find the net torque.

2. How do I find the center of mass of an object?

The center of mass of an object can be found by balancing the object on a pivot point and marking the point where it balances. This point is the center of mass, and it can also be calculated mathematically by finding the average of all the individual masses in the object.

3. How does the direction of the force affect torque?

The direction of the force relative to the axis of rotation affects the torque. A force applied parallel to the axis of rotation will not create any torque, while a force applied perpendicular to the axis will create the maximum torque. The greater the angle between the force and the axis, the smaller the torque will be.

4. How does the lever arm affect torque?

The lever arm is the distance between the axis of rotation and the point where the force is applied. The longer the lever arm, the greater the torque will be. This is because a longer lever arm creates a greater perpendicular distance between the force and the axis, resulting in a greater torque.

5. How do I use the right-hand rule to determine the direction of torque?

To use the right-hand rule, simply point your thumb in the direction of the force and curl your fingers towards the axis of rotation. The direction your fingers are pointing is the direction of the torque. This rule follows the direction of angular velocity in a clockwise direction.

Similar threads

  • Advanced Physics Homework Help
Replies
5
Views
2K
  • Introductory Physics Homework Help
3
Replies
95
Views
4K
  • Advanced Physics Homework Help
Replies
1
Views
795
  • Mechanical Engineering
Replies
9
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
2K
Replies
31
Views
740
  • Advanced Physics Homework Help
Replies
11
Views
1K
  • Introductory Physics Homework Help
Replies
18
Views
804
  • Advanced Physics Homework Help
Replies
14
Views
3K
Back
Top