Dynamics- Angular Impulse and Momentum Problem

Click For Summary
SUMMARY

The discussion centers on a dynamics problem involving a 30-kg reel mounted on a 20-kg cart, subjected to a force of P=50 N. The goal is to determine the velocity of the cart and the angular velocity of the reel after 4 seconds, using the radius of the reel's inner hub (150 mm) and the radius of gyration (250 mm). The impulse equation presented, P*r*t=Iω2+mv2, requires a second equation to relate angular velocity (ω2) and linear velocity (v2) due to the presence of two variables. The torque τ acting on the reel is defined as τ = P*r1, leading to a straightforward solution if the assumptions about forces and torque are correct.

PREREQUISITES
  • Understanding of dynamics principles, specifically angular momentum and impulse.
  • Familiarity with torque calculations and their relationship to angular acceleration.
  • Knowledge of moment of inertia calculations, particularly I=mk².
  • Ability to apply Newton's second law to rotational systems.
NEXT STEPS
  • Study the relationship between linear and angular motion in dynamics.
  • Learn about the application of Newton's second law in rotational systems.
  • Explore torque and its effects on angular acceleration in mechanical systems.
  • Investigate the concept of impulse and its role in solving dynamics problems.
USEFUL FOR

Students and professionals in mechanical engineering, physics enthusiasts, and anyone involved in solving dynamics problems related to rotational motion and impulse-momentum principles.

CylonToaster
Messages
2
Reaction score
0

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 \intMGdt=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?
 

Attachments

  • dynamics.png
    dynamics.png
    7.5 KB · Views: 763
Physics news on Phys.org
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.
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
4K
Replies
1
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
5
Views
5K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
5
Views
1K
Replies
14
Views
3K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K