Screen 1

Screen 1 shows three pictures illustrating forces, and also includes the objectives and key vocabulary for the lesson.

1. Read out the text. Do the children know these words? Can they explain what they mean? Don't provide the answers yet, but make a note of what they say, so you can ask them again at the end of the activity and see if their ideas have changed.

Screen 2

Screen 2 shows four pictures of objects that are moving because a force has been applied to them.

1. Ask the children to read out the text.
2. Look at the kite picture and ask "What are the forces acting on the kite?" The children may mention gravity, air resistance, hand pulling the string down, and wind pulling the kite up.
3. Decide which arrow direction is most suitable. In Use Mode, select the arrow and drag it into place on the kite picture. Use purple-coloured arrows to describe the direction of one force, and green-coloured arrows to describe the direction of an opposite force. For each arrow, ask: "What is applying this force to the object?"
4. Repeat for the other objects. For the cricket ball and the football, point out that the force is applied initially to make the object move. However, as soon as the ball has left the bat/boot the force is no longer being applied. "What other forces may be acting on the balls after they have been hit/kicked?" (gravity, air resistance) "Could these be shown by arrows as well?"

Screen 3

Screen 3 shows two pictures of a moving police car. In the first picture the car is moving forwards; in the second picture it is moving backwards.

1. Explain that when two forces are acting on an object, we can use arrows of different sizes to show which force is the strongest.
2. Ask the children to look at the forces in the first picture. Which is the greatest force, that of the engine or that of the air resistance? How do they know this from the picture? (by the relative size of the arrows).
3. In Use Mode, click on the car and watch it move forwards.
4. Now look at the second picture. Ask the children to point the way the car is travelling this time.
5. Click on the car to watch it reverse.
6. Ask a child to select and drag the appropriate arrows on to the picture, to show that the force from the engine (in reverse) is greater that the force of the air resistance.
7. Ask the children to try and explain what they think is happening in each picture. In each case the car is moving because the opposing forces are not equal.

Screen 4

Screen 4 shows two pictures of a boat. In one the boat is sinking; in the other it is not.

1. Ask the children to read out the black text. Make sure they understand that gravity is a force that pulls things downwards towards the Earth, and that upthrust is the force that the water is applying to push the boat back upwards in the water.
2. Look at the slowly sinking boat. Ask the children "What is happening to the boat?"
3. Ask "How can you represent the forces using the arrows provided?" Get a child to drag arrows on to the pictures to show the forces of gravity and upthrust. (When the boat has sunk to the bottom, you can re-start the sinking by clicking on it in Use Mode.)
4. Now click on the second boat. "What is happening?" The boat is floating, bobbing gently up and down on the ocean.
5. Ask "How can you represent this using the arrows provided?" Get a child to drag the arrows on to the pictures to show the forces of gravity and upthrust.
6. Ask the children to explain what they think is happening. Explain to the children that, in the case of the floating boat, the forces must be the same size, as the boat is neither moving up nor down. In this case we describe the forces as being 'balanced'.

Screen 5

Screen 5 shows two pictures of a submarine in the water. Use this screen to consolidate the concepts of gravity and upthrust introduced in Screen 4.

1. Click on a submarine and watch what it does.
2. Ask a child to describe the forces acting on the submarine to make it behave in that way, and to show these forces using the arrows.
3. Repeat for the other submarine.