Dynamics- Angular Impulse and Momentum Problem

In summary, the problem involves a 30-kg reel mounted on a 20-kg cart with a cable wrapped around the reel's inner hub with a radius of 150mm. There is a force of 50 N acting on the cable, and the goal is to determine the velocity of the cart and the angular velocity of the reel after 4 seconds. The radius of gyration of the reel about its center of mass is given as 250 mm, and the size of small wheels is neglected. The two main equations involved are IG*ω1+Σ \intMGdt=IG*ω2 and P*r*t=Iω2+mv2, with two unknown variables, ω2 and v2.
  • #1
CylonToaster
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Homework Statement


The 30-kg reel is mounted on the 20-kg cart. If the cable wrapped around the inner hub of the reel, with radius 150mm, is subjected to a force of P=50 N, determine the velocity of the cart and the angular velocity of the reel when t=4 sec . The radius of gyration of the reel about its center of mass O is kO = 250 mm. Neglect the size of the small wheels.
Attached is a picture

Homework Equations


IG1+Σ [itex]\int[/itex]MGdt=IG2


The Attempt at a Solution


I=mk2=1.875 kg/m2
So my impulse equation solves down to:
P*r*t=Iω2+mv2
I end up with 2 variables and 1 equation. What is my missing equation, or how do I relate ω2 and v2?
 

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  • #2
Sorry no one has responded thus far.

Not my specialty, but I would base my computations on two interpretations:

1. Irrespective of the motion of the cart, there is a constant torque τ applied to the reel, with resulting angular acceleration, that torque being τ = P*r1 where r1 = radius of inner hub. Thus θ'' = τ/I and you have already computed I, hopefully correctly.

2. The only force applied to the cart + wheel assembly is P. So P = Mx'' for the assembly where M = total assembly mass (50kg).

If these observations hold then the problem is actually quite straightforward. I think they do. I notice that your "impulse equation" has inconsistent dimensions within it.
 

FAQ: Dynamics- Angular Impulse and Momentum Problem

What is angular impulse?

Angular impulse is a measure of the change in angular momentum of an object. It is calculated by multiplying the average torque applied to an object by the time interval over which it acts.

How is angular impulse different from linear impulse?

Angular impulse is the change in angular momentum, while linear impulse is the change in linear momentum. Angular impulse applies to objects that rotate around an axis, while linear impulse applies to objects that move in a straight line.

How do you calculate the angular momentum of an object?

The angular momentum of an object is calculated by multiplying its moment of inertia by its angular velocity. The moment of inertia is a measure of an object's resistance to changes in rotation.

What is the law of conservation of angular momentum?

The law of conservation of angular momentum states that in a closed system, the total angular momentum remains constant. This means that if no external torques act on a system, the total angular momentum of the system will not change.

How can angular impulse and momentum be applied in real-world situations?

Angular impulse and momentum are used in many real-world situations, such as analyzing the movement of objects in sports, designing machines and vehicles that rotate, and understanding the behavior of celestial objects in space. They are also important in the study of biomechanics and the motion of the human body.

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