Module 3 - Equilibrium Flashcards

1
Q

Define Centre of Mass

A

The point where the mass of an object appears to acts

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2
Q

Define Centre of Gravity

A

The point where the weight of an object appears to acts

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3
Q

What are factors that affect the stability of a object

A
  • Having a wider base (as it increases the tilt required to make the CoG act outside of the base)
  • Having a lower centre of gravity (as it would take more tilt to act outside of the base)
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4
Q

How to find the Centre of Gravity for uniform objects

A
  • Find where the lines of symmetry of the object meet
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5
Q

How to find the Centre of Gravity for non-uniform objects

A
  • Suspend object from a pin and it will naturally hang stationary about its CoG.
  • Draw a line vertically down the pin
  • repeat this for another point on the object
  • The CoG will be where the two lines meet
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6
Q

Why might some objects Centre of Gravity not act through its middle

A

If the distribution of the mass of the object is not uniform.

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7
Q

What is a Moment

A

The turning effect of a force.

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8
Q

What is the equation for Moments

A

The Moment of a force = The Perpendicular Distance (of the line of action of the force) from the pivot X The Force

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9
Q

What is meant by the perpendicular distance from the pivot

A

The Distance between the line of action of the force and the Pivot Point

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10
Q

What is the unit for Moments

A

Nm [Newton-Metre]

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11
Q

What is the Principle of Moments

A

“For a system in Equilibrium, the sum of the clockwise moments are equal to the sum of the anti-clockwise moments”

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12
Q

How do you find 2 Forces of opposing direction from a Moments system when both are unknown

A

Take 1 of the unknown forces to be the pivot and use the principle of moments to find the other force
- Repeat for the 2nd Force or use knowledge of the resultant force to find the 2nd Force

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13
Q

What is meant by a force couple

A
  • A pair of forces that subscribe to the following:
    1. Are equal in magnitude
    2. Opposite in direction
    3. Parallel but act along different lines
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14
Q

What is meant by the torque of a couple

A

The turning effect of a force couple

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15
Q

What is the equation of the torque of a couple

A

t (Torque) = F (Magnitude of one Force) x d (Perpendicular Separation Between Forces)

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16
Q

What are the requirements for equilibrium of an object under the action of
forces and torques

A

For a system in equilibrium:
1. The sum of the anticlockwise moments about any point = the the sum of the clockwise moments about the same point
2. The net force = 0N

17
Q

How do you find the resultant force of 3 coplanar forces given 2 and that the system is in equilibrium

A

Draw the first 2 tip to tail, and the 3rd force must be equal and opposite to the resultant of the first 2 forces.