Force & Slope Question: Issues with (ii)

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Discussion Overview

The discussion revolves around calculating the forces involved in accelerating a wagon on an incline, specifically addressing issues related to torque and the forces required for both horizontal and inclined movement. Participants explore the necessary calculations to determine these forces under varying conditions.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant expresses difficulty in calculating the force needed to accelerate the wagon, indicating they have successfully worked out part (i) but struggle with part (ii).
  • Another participant questions the force required to accelerate the wagon on a flat surface, suggesting that without acceleration, the force is uncertain.
  • There is a reference to a problem statement that specifies accelerating the wagon from rest to a certain speed over a distance, which is noted by multiple participants.
  • One participant confirms they have calculated the acceleration but are unsure about the correct force needed.
  • Another participant suggests calculating the force necessary to move the wagon up the incline and adding it to the force required for acceleration.
  • Participants engage in calculations involving mass, gravitational force, and sine of the incline angle, with one participant initially providing an incorrect value due to using radians instead of degrees.
  • There is a correction regarding the sine of the angle, leading to a revised calculation of the force.
  • Another participant acknowledges the complexity they added to the problem and expresses relief at arriving at a solution.
  • A final participant raises a question about the torque needed for the drum and its relation to the total torque required by the motor, suggesting a potential connection but not confirming it.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct approach to calculating the forces involved, and there are multiple competing views regarding the necessary calculations and their implications.

Contextual Notes

Some calculations depend on the correct interpretation of angles (degrees vs. radians), and there are unresolved aspects regarding the total torque needed by the motor and how it relates to the forces discussed.

smr101
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I've worked out (i), having problems with (ii). I know that the torque will be force x 0.75 but I haven't had any success in working out the force in the first place.
 
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What's the force required to accelerate the wagon if there's no incline?
 
Bystander said:
What's the force required to accelerate the wagon if there's no incline?

Without an acceleration, I'm not sure.
 
smr101 said:
Without an acceleration, I'm not sure.
From the problem statement, "... accelerate the wagon from rest to 2.6 m/s over a distance of 8.2 m at constant acceleration ..."
 
Bystander said:
From the problem statement, "... accelerate the wagon from rest to 2.6 m/s over a distance of 8.2 m at constant acceleration ..."

Right I've got the acceleration but I'm not getting the correct force. You're saying the force needed to work out the torque is when there is no incline?
 
smr101 said:
when there is no incline?
No. You've got the force to do the acceleration? Can you calculate the force necessary to move the wagon up the incline? Add them.
 
Bystander said:
No. You've got the force to do the acceleration? Can you calculate the force necessary to move the wagon up the incline? Add them.

F = ma
= 1920 x 0.41
= 787.2

Fw = mgsinangle
= 1920 x 9.81 x sin10
= -10246.7
 
smr101 said:
= 1920 x 9.81 x sin10
= -10246.7
Don't just punch numbers into a calculator and blindly accept the number that comes out. What's the sin of 10°?
 
Bystander said:
Don't just punch numbers into a calculator and blindly accept the number that comes out. What's the sin of 10°?

Ah, I was in radians...

Fw = mgsinangle
= 3270.7
 
  • #10
Better.
 
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  • #11
Bystander said:
Better.

Then just add the Ff to that and the Fu I've got it... Thanks, I've made that much more difficult than it should have been!
 
  • #12
I'm assuming the torque needed for the drum, which would be used to calculate the total torque needed by the motor is the same? Just different values.
 

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