How Is the Driving Torque Calculated for a Hoist Drum in Rotational Dynamics?

In summary, a mine cage of mass 4 tonne is being raised with an acceleration of 1.5m/s^2 using a hoist drum of 1.5m diameter. The drum's mass is 750kg and its radius of gyration is 600mm. The effect of bearing friction is equivalent to a torque of 3kNm at the hoist drum. The driving torque required on the drum is 37440Nm. To find the deceleration of the load and how far it travels before coming to rest, the equation of F = M*A is used, resulting in an acceleration of 9.64m/s^2. The error in calculating the driving torque is not accounting for the mass
  • #1
MMCS
151
0
A mine cage of mass 4 tonne is to be raised with an acceleration of 1.5m/s^2
using a hoist drum of 1.5m diameter. The drum’s mass is 750kg and its radius of gyration is 600mm.The effect of bearing friction is equivalent to a torque of 3kNm at the hoist drum. What isthe driving torque required on the drum ? If the driving torque ceases when the load is
moving upwards at 6m/s, find the deceleration of the load and how far it travels before
coming to rest.

My question is the second part, to find the deceleration.

i already know the answer to the first part, which is the torqure required, which is 37440Nm

I get F = M*A >> A = F/M >>> 37440/4000 = 9.36m/s^2

but i have the answer to be 9.64m/s^2
 
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  • #2
MMCS said:
the answer to the first part, which is the torqure required, which is 37440Nm
Typo? I make 37470.
I get F = M*A >> A = F/M >>> 37440/4000 = 9.36m/s^2

What does dividing a torque by a mass give you?
Draw the free body diagrams, putting in unknowns for tension and acceleration. Develop the equations for the cage and the drum separately.
(It doesn't happen here, but in general you ought to check the tension has not gone negative. It could with greater drum friction.)
 
  • #3
Going back to the first question, could you tell me the error in my calculation to work out driving torque

mass*acceleration*radius + mass*gravity*radius + inertia * radius of gyration2 + friciton torque = driving torque

4000*1.5*0.75 + 4000*9.81*0.75 + 750*0.62 + 3000 = 37.2*103
 

Related to How Is the Driving Torque Calculated for a Hoist Drum in Rotational Dynamics?

1. What is rotational dynamics of cage?

Rotational dynamics of cage is the study of the motion and forces involved in the rotation of a rigid body, specifically a cage-like structure. It involves analyzing the angular acceleration, angular velocity, and torque acting on the cage to understand its rotational behavior.

2. How is rotational dynamics of cage different from regular rotational dynamics?

Regular rotational dynamics deals with the motion of a single rigid body, while rotational dynamics of cage involves the motion of multiple rigid bodies connected in a cage-like structure. This adds complexity to the analysis as the motion of one body affects the motion of the others.

3. What are some real-life applications of rotational dynamics of cage?

Rotational dynamics of cage is commonly used in engineering and physics to understand the behavior of complex systems such as helicopters, satellites, and robots. It is also relevant in sports, as the motion of a gymnast or diver can be analyzed using principles of rotational dynamics of cage.

4. What factors affect the rotational dynamics of cage?

The rotational dynamics of cage can be affected by factors such as the mass distribution of the bodies within the cage, the shape and size of the cage, and external forces such as friction and air resistance. The initial conditions, such as the starting position and velocity, also play a role in the rotational behavior.

5. How is rotational dynamics of cage related to other branches of physics?

Rotational dynamics of cage is closely related to other branches of physics, such as classical mechanics and Newton's laws of motion. It also has connections to rotational motion in fluid dynamics and the principles of conservation of angular momentum. Additionally, it is often used in conjunction with other fields, such as structural engineering, to analyze the stability and dynamics of structures.

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