Moments and Levers

​Moments of a force

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1. State what moments are

2. Calculate moments

3. State when moments are balanced or unbalanced using calculations

4. Do a quick quiz​

Learning Outcomes

Starter Activity

​I need two students for this, a boy and a girl

With your right hand only, follow the teacher's instruction​

At what point did you put more effort into the opening and closing of the door?

What is the moment of a force?

A force or a system of forces may cause an object to rotate. This turning effect of a force around a specific point (pivot) is called the moment of a force.

Open Ended

What is a pivot? In the case of the door experiment, what part of the door is the pivot?

2. The perpendicular distance from the pivot to the force

​1. The size of the force

What is the size of a moment dependent on?

Multiple Choice

To increase the moment of a force, you can do all of the following EXCEPT?

• Increase the distance from the pivot

• Increase the force required to turn the object

• Decrease the distance from the pivot

• None of the above

​How to calculate the moment of a force

Multiple Choice

What is a moment?

• The speeding up of a force

• The turning effect of a force

• The spinning effect of a force

• The movement of a force

When you want to do any calculations in physics, remember VESRAU

Example 1:

​A force of 100N is applied to a bolt, 0.5m from the pivot. Calculate the moment of the force

V-Values F= 100N d= 0.5m

E- Equation M = F x d

S- Substitute M= 100N x 0.5m

R-Re-arrange - In this case, it is not necessary. Why?​

A- Answer - M= 50

U-Unit - M = 50Nm​

​Example 2

A force of 2000N is applied by a crane and creates a 40000Nm moment. Calculate the distance from the pivot,

V-Values F= 2000N M= 40000Nm

E- Equation M = F x d

S- Substitute 40000Nm= 2000N x d

R-Re-arrange - d= 40000Nm /2000N

A- Answer - d= 20

U-Unit - d = 20m

Subject | Subject

Multiple Choice

A force of 30N is applied to a door, 0.2m from the pivot. Calculate the moment of the force.

• 6Nm

• 0.6Nm

• 6N/m

• 60N/m

​Do this in your notebook.

Show your workings using VESRAU.

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A crane creates a 35000Nm moment when the load is 5m away from the pivot. Calculate the force​

Subject | Subject

Multiple Choice

A spanner tightens a bolt with a moment of 240Nm. Calculate the force needed to loosen the bolt when you hold the spanner 40cm away from the pivot.

• 60N

• 600N

• 6000N

• 6N

Balancing Moments

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​Anti-clockwise moments = Clockwise moment​

Multiple Choice

For an object to be balanced...

• Left side moment is equal to right side moment

• Clockwise moment is equal to anti-clockwise moment

• Anti-clockwise moment is smaller than clockwise moment

• Clockwise moment is larger than anti-clockwise moment

Open Ended

Is this crane balanced? Give a reason for your answer

​This task requires you to work with a partner, Work with the person by your side.

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This crane is balanced,

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1, What is the weight of the load in this question?

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2. How did you solve it?

Open Ended

Rajiv puts a piece of wood on a pivot. He adds weights at different distances from the pivot. The wood balances. Calculate the weight labeled A in the diagram.

Open Ended

Mike and Oliver sit on a see-saw. Mike is smaller than Oliver but the see=saw balances. Explain why it balances using the principles of moments.

Multiple Choice

What is the weight needed to balance this?

• 0.6N

• 6N

• 60N

• 600N

Multiple Choice

What is the distance needed to balance this?

• 45m

• 0.45m

• 4.5m

• 450m

1. State what moments are

2. Calculate moments

3. 3. State when moments are balanced or unbalanced using calculations

4. Do a quick quiz​

Learning Outcomes

Open Ended

What part of the lesson was the easiest to understand?

Open Ended

What part of the topic was the most difficult to understand?