P3 - Turning Forces

Question 0

How do you calculate the moment?

Answer 0

M = F * d

Moment = force * perpendicular distance from line of action of the force to the pivot

Question 1

What is a moment?

Answer 1

The turning effect of a force

Question 2

What is the unit of a moment?

Answer 2

Newton-metres (Nm)

Question 3

What is the line of action?

Answer 3

The direction of the force

Question 4

How do you get the maximum moment?

Answer 4

The direction of the force has to be perpendicular to the object being pushed so that d in the formula (perpendicular distance from line of action of the force to the pivot) is as high as possible

Question 5

What is the centre of mass?

Answer 5

The point of an object at which the whole mass is concentrated

Question 6

What happens when an object is swinging from a suspension and why?

Answer 6

The object will swing until its centre of mass is vertically below the point of suspension

Now there is no moment because the pivot is in line with the line of action of the force

Question 7

Describe how you find the centre of mass of a flat shape

Answer 7

Suspend the shape and a plumb line from the same point and wait until they stop moving

Draw a line along the plumb line

Do the same thing again but suspend the shape from a different pivot point

The centre of mass is where the 2 lines cross

Question 8

What is balance in terms of moments?

Answer 8

When the clockwise moment and anti-clockwise moment are equal so that there is no resultant moment

Question 9

What are levers and why do they work?

Answer 9

Levers use moments to make it easier for us to do work (like lifting an object)

They work by increasing the distance from the pivot at which the force is applied meaning that less force is needed to achieve the same moment

In short, they decrease the force needed by increasing the distance

Question 10

What is a stable object?

Answer 10

One that will not easily tip over

Question 11

When do objects tip over?

Answer 11

When the line of action of the weight of the object lies outside of the base of the object

Question 12

What 2 things make an object stable and why?

Answer 12

A wide base and a low down centre of mass

Both of these factors make the angle needed to make the line of action lie outside of the base of the object higher and therefore tip over the object