Forces in Motion

YOU ARE LEARNING:

Isolated Objects

You will learn why it is useful to isolate objects or systems that have forces acting on them.

The image shows the forces acting on an isolated object (the skydiver).

Only the forces acting upon the skydiver are shown in the diagram. This is how we isolate an object.

Which force represents weight ?

What type of force is F1?

What is the direction of the resultant force?

Will the skydiver be experiencing a change in velocity?

We often isolate objects or systems of interest to show or describe the forces acting upon them. This means we show the forces acting on the object, but not any forces that the object might exert on anything else.

If an isolated system means more than one object, what might a force system refer to?

Which forces would constitute the system of forces acting on an aeroplane in flight? Pick all the options below that you think are correct.

You can select multiple answers

When using diagrams to show the system of forces acting on an isolated object, it is important to draw the vectors representing the forces to scale so that we can visualise the relative magnitude and direction of the forces. Without a scaled diagram, we could not find the resultant force!

Free body diagrams are used to show the system of forces acting on an isolated object.

Here is an example of a simple free body diagram to represent the forces acting upon a boat.

Forces 2 and 4 are acting in opposite directions, and are represented by vectors of the same length. What does that tell us about the magnitude of the forces?

Forces 1 and 3 are not balanced and the boat is accelerating forward. Which force is the driving force?

You want to draw a diagram to show the system of forces acting on a car. If you know that the driving force is $2000\space N$ , what would be the most appropriate scale to use?

You want draw a diagram to show the system of forces acting on a car. You are using the scale $1\space cm = 200\space N$ and you know that the driving force is $3200\space N$ . What length is the arrow you draw to represent the driving force?