Balanced and Unbalanced Forces

Balanced and Unbalanced Forces

Multiple Choice

Identify the definition of a balanced force.

• A force that causes an object to speed up

• A force with an equal and opposite force acting on the same object

• A force with an equal force acting in the same direction

• A force that causes an object to stop moving

• I'm not sure

Multiple Select

Determine which two of the following have balanced forces acting on them.

• A cat sleeping in a chair

• A rocket speeding up as it launches into space

• A mug resting on a bench

• A basketball speeding up as it falls through the air

• I'm not sure

When sitting on a chair, the force of gravity pulls you downwards, towards Earth. A support force from your chair acts upwards and balances the downwards force of gravity.

​Balanced forces don’t always mean that the object is stopped: it might be travelling at the same speed without changing directions.

Balanced Forces

Poll

The figures in the image on the right are both pulling with equal strength in opposite directions. We can see this from the size and direction of the arrows.

What do you think will happen to the trolley when these two forces are applied to it?

• The trolley will move to the right

• The trolley will move to the left

• The trolley will not move

• The trolley will move side to side continuously

Follow these steps on the next page:

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Tug of War Activity

1. Drag one small blue figure and one small red figure onto the rope.
2. Press "Go!" when you are ready to run the interactive.
3. Press the orange reset button in the right-hand corner to start again.

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Open Ended

What happened?

Did your prediction match what happened?

Labelling

Identify the forces acting on the apple.

Drag labels to their correct position on the image

Tension

Stretch

Normal Force

Gravity

Multiple Choice

Balanced forces can only act on objects that are not moving.

• True

• False

• I'm not sure

Multiple Choice

Look at the image of the skydiver above to determine the correct end to the sentence.

When air resistance and gravity are balanced, the skydiver will:

• Stop falling

• Speed up

• Slow down

• Continue to fall at a constant speed

• I'm not sure

What do we call it when a force does not have an equal and opposite force?

A force that doesn't have an equal and opposite force acting on the same object is called an unbalanced force.

When the forces acting on an object are not balanced then the object's motion will change.

Unbalanced Forces

Multiple Choice

Select the best definition of an unbalanced force.

• A force that is equal in size and opposite in direction to another force

• A force that has no effect on an object's motion

• A force without an equal and opposite force acting on the same object

• I'm not sure

Multiple Select

Determine which two of the following objects have unbalanced forces acting on them.

• A car that is speeding up

• A laptop resting on a desk

• A rolling ball that is slowing down

• An airplane travelling at a constant speed

• I'm not sure

Labelling

Classify the forces as balanced or unbalanced.

Drag labels to their correct position on the image

Balanced

Unbalanced

Labelling

Classify the forces as balanced or unbalanced.

Drag labels to their correct position on the image

Unbalanced

Balanced

The image on the right shows two small figures pulling left and one small figure pulling right.

The arrows indicate that the forces are opposite but unequal.

Predict what will happen...

Poll

Predict what you think will happen once the figures start pulling.

• The trolley will move to the right

• The trolley will move to the left

• The trolley will not move

• The trolley will move side to side continuously

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Another Tug of War Activity

Use the interactive on the next slide to change the arrangement of the figures.

This time you must create an unbalanced force that moves the trolley to the right.

​Show me when you're done!

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