Finding Acceleration and Reaction Forces in Rotating Thin Rod on a Hinge

In summary, the problem involves a thin rod hanging vertically from a fixed hinge and a horizontal impulsive force being applied to it. The questions ask for the acceleration of the center of mass, the horizontal force exerted by the hinge, the acceleration of a point at the midpoint of the rod, and the point where the impulse can be applied for the hinge to exert no horizontal force. Using the equations for torque and moment of inertia, the solution for part (a) is found to be 3F/2M.
  • #1
mli
2
0

Homework Statement


A thin rod of mass 0.620 kg and length 1.08 m is at rest, hanging vertically from a strong, fixed hinge at its top end. Suddenly, a horizontal impulsive force (14.2 i ) N is applied to it.
(a) Suppose the force acts at the bottom end of the rod. Find the acceleration of its center of mass.
(b) Find the horizontal force the hinge exerts.
(c) Suppose the force acts at the midpoint of the rod. Find the acceleration of this point.
(d) Find the horizontal hinge reaction force.
e) Where can the impulse be applied so that the hinge will exert no horizontal force? This point is called the center of percussion.

Homework Equations


[tex]\Sigma\tau = FL =I\alpha \\ I=1/3 ML^2 \\ \alpha=a_{T}/L[/tex]

The Attempt at a Solution


[tex]FL=1/3 ML^2\alpha[/tex]
Rearranging for alpha gives
[tex]\alpha=3F/ML[/tex]

I'm stuck on part a. I can work out the tangential acceleration but it's looking for the acceleration at the com. I can't recall any equations about the relationship between tangential and center of mass acceleration and can't seem to find anything on google either. Thank you in advance!
 
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  • #2
Do you know how
angle is related to position ?
angular speed is related to velocity ?
angular acceleration is related to acceleration ?

Perhaps you can find yourself a hint by looking at the dimensions ?

google (angular speed linear speed)
 
  • #3
Oops, thanks. Since α=atangentialL, α=acomL/2 right? That gives acom = 3F/2M
 

1. What is a thin rod rotating on a hinge?

A thin rod rotating on a hinge refers to a physical system in which a thin rod or bar is attached to a fixed point (hinge) and can rotate around that point. This system is commonly used in physics experiments to study rotational motion and torque.

2. How does the rotation of a thin rod on a hinge work?

The rotation of a thin rod on a hinge is governed by the principles of rotational motion and torque. The applied force on one end of the rod creates a torque, causing the rod to rotate around the hinge. The rotation will continue until an equal and opposite torque is applied.

3. What factors affect the rotation of a thin rod on a hinge?

The rotation of a thin rod on a hinge can be affected by various factors, such as the length and mass of the rod, the angle of the applied force, and the distance between the force and the hinge. The properties of the hinge, such as its friction and stiffness, can also impact the rotation.

4. How is the rotational speed of a thin rod on a hinge measured?

The rotational speed of a thin rod on a hinge can be measured by attaching a sensor or a marker to the rod and using a high-speed camera to capture its movement. The number of rotations per unit time can then be calculated to determine the rotational speed.

5. What are the real-world applications of a thin rod rotating on a hinge?

A thin rod rotating on a hinge has various applications in the real world, including door hinges, pendulums, and mechanical joints in machines. It is also used in scientific experiments to study rotational motion and torque, and in engineering to design and test structures and mechanisms that involve rotational motion.

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