Turning Forces Flashcards
What happens when you push down on a door handle?
The handle turns.
What occurs when you push down on the pedal of a bicycle?
The pedal turns
What is a lever?
A lever is an object that turns around a pivot when a force is applied.
What is a pivot?
The pivot is the point around which a lever turns.
Where is the lever and pivot shown in everyday life?
In the picture of the bicycle pedals or in the bending of your arm.
In your body, which part acts as a lever and what is the pivot?
The arm acts as a lever, and the elbow is the pivot.
What describes the turning effect of a force?
The moment of a force.
What two factors does the moment of a force depend on?
- The size of the force.
- The distance between where the force acts and the pivot.
How does the size of the force affect the moment?
The bigger the force, the bigger the moment.
How does the distance between the force and pivot affect the moment?
The greater the distance, the greater the moment.
What is the equation to calculate a moment?
Moment = Force × Distance
What does the distance in the moment equation represent?
The distance from the pivot to the position where the force acts.
What is the unit of force?
Newton (N).
What is the unit of distance in the moment equation?
Metre (m).
What is the unit of moment?
Newton metre (Nm).
How should you write the unit of moment correctly?
Use an upper case “N” for newton and a lower case “m” for metre (Nm).
How should you write the unit of moment correctly?
Use an upper case “N” for newton and a lower case “m” for metre (Nm).
Worked Example 1: A pulling force of 35 N is needed to open a door. The distance from the door handle to the pivot is 0.8 m. How do you calculate the moment?
Moment = Force × Distance = 35 × 0.8 = 28 Nm.
Worked Example 2: A weight of 20 N acts on an arm 0.25 m away from the pivot. How do you calculate the moment?
Moment = Force × Distance = 20 × 0.25 = 5 Nm.
What type of lever is a seesaw?
A seesaw is a type of lever.
How does a seesaw work in terms of forces?
People sit on either side of the pivot, making the lever turn one way and then the other.
When is a seesaw balanced?
A seesaw is balanced when the moments on both sides of the pivot are equal and opposite.
Marcus, with a weight of 600 N, sits at a distance of 2 m from the pivot of a seesaw. Arun has a weight of 800 N. Where should Arun sit to balance the seesaw?
Marcus’s moment = 600 N × 2 m = 1200 Nm.
• To balance the seesaw, Arun’s moment must also be 1200 Nm.
• Using the formula:
• Distance = Moment / Force = 1200 Nm / 800 N = 1.5 m.
How do you calculate the distance needed for balance on a seesaw?
Use the formula: Distance = Moment / Force.
What is meant by the word “moment” in physics?
The moment of a force describes the turning effect of that force.
What is the equation that links moment, force, and distance?
Moment = Force × Distance.
What is the unit of moment?
Newton metre (Nm).
In the spanner and nut diagram, which arrow should Jon push to produce the largest moment to turn the nut?
The letter corresponding to the direction that maximizes the perpendicular distance from the pivot.
Why should Jon push in the chosen direction to produce the largest moment?
The force should be applied perpendicular to the spanner to maximize the distance from the pivot, producing the largest moment.
How do you calculate the moment caused by Sofia pushing on a door handle with a force of 4 N at a distance of 0.12 m?
Moment = Force × Distance = 4 N × 0.12 m = 0.48 Nm.
How do you calculate the force needed at position F to produce a moment of 1.8 Nm on a bicycle brake lever with a distance of 0.09 m?
Force = Moment / Distance = 1.8 Nm / 0.09 m = 20 N.
How do you calculate the force needed at position F to produce a moment of 1.8 Nm on a bicycle brake lever with a distance of 0.09 m?
Force = Moment / Distance = 1.8 Nm / 0.09 m = 20 N.
Zara weighs 450 N and sits 1.5 m from the pivot on a seesaw. Sofia weighs 500 N. How far must Sofia sit from the pivot to balance the seesaw?
Using the balancing moment equation:
• Zara’s moment = 450 N × 1.5 m = 675 Nm.
• Sofia’s distance = 675 Nm / 500 N = 1.35 m.
