Initial problem: Why do things move?
Background
When we move things we push or pull them. Squeezing, stretching and twisting are all types of pushes and pulls. A big push or pull will have a greater effect on the movement of an object than a small push or pull.
Assessment: Suitable techniques include
• teacher observation: willingness to try different ideas; willingness to work with others
• portfolio: annotated drawings of work • concept maps.
Resources
Lesson 1: Collection of moving things in the classroom; pencil case with a zip, toy telephone with a circular dial, yo-yo; toys, cars, pram, shopping trolley, clocks, egg beaters, spinning tops, tricycle or bicycle.
Lesson 2: Sponge, cloth, rubber bands, balloon, squeezy bottles, ball.
Lesson 1: Pushing and pulling
Children make collections of things that move in the classroom. Ask the children to consider:
• Can you make these things move?
• What do they need to make them move? (push/pull) • Why does the toy car stop moving?
Children can draw the things that move, cut out pictures or make a collage of things that move at home and in the environment.
Sort into sets according to what they need to make them move.
• Which things need a push to move? • Which things need a pull?
Ask children to think of other ways of moving the toys. Some children may try blowing the toys or placing them on inclined or flat surfaces. They can then try to make the moving things go faster or slow down.
Encourage children to find different ways of stopping an object.
Children observe objects that move with wheels, such as a pram, tricycle, bicycle, skateboard, wheelbarrow and toy cars. Consider if wheels help objects to move:
• Can the toys with wheels move quickly? • Can they move a long distance? • Do they need a big push/pull to move?
Explore how a large heavy box of toys can be moved. Can we put something underneath it to make it move? Encourage children to try rollers: tinfoil rolls, drinks cans glued together to make a large roll, brush-handles, dowels and cylindrical objects.
Starting points
Development of
lesson
Extension of
lesson: follow-up
activities
Lesson 2: Forcing things to change shape
Provide the children with different objects, some that can change shape and some that cannot. Allow the children adequate time to explore how some of the objects can change shape.
Children should be asked to handle the different objects and change their shape by twisting, squeezing or stretching. • Can you make this object change shape?
• How can you make it change shape?
Sort the objects into two groups. In one circle draw the objects that change shape and in another circle draw the objects that don’t change shape. Children should be asked to discuss with each other the pushes and pulls involved in changing the shape of an object: • When you squeeze a sponge are you pushing or pulling? • When you stretch the sponge are you pushing or pulling? • When you squash a can are you pulling or pushing? • When you stretch a rubber band are you pulling or pushing?
Collect materials that go back to the same shape after they have been squeezed or pulled.
Section 5 Appr oache s and me thodologie s
Friction
Push a toy car or roll a marble across a table and observe as it slows down and comes to rest. The car stops because there is a force acting on it. Friction is the force that opposes the movement of an object. There are several forces acting on the moving car:
• the forward force from the push that was given to the car. This causes the wheels of the car to turn. The wheels then push on the surface of the table
• the force of friction between the tyres and the surface
• air resistance.
Objects that move through the air experience the frictional force of the air, which acts in the opposite direction to their movement. Air resistance acts against gravity on falling objects. As the speed of the falling object increases, the air resistance increases.
Exemplar 32 illustrates some approaches
to exploring friction with children in
third and fourth classes. This activity is
also appropriate for senior classes.
Gravity
All objects attract one another. The force of attraction which an object exerts is in proportion to its mass. The Earth has a large mass, and so the force of attraction between it and other objects is big, and this force pulls objects to the Earth. This force is called the ‘weight’ of an object. The weight of an object is a measure of how much the Earth pulls on it.
When you lift a bucket two forces are at work. These are the upward force or pull exerted by you and the downward pull of gravity.
Appr oache s to learning about for ce s
Falling objects
Two objects, such as a pebble and a block, released from the same height above ground will fall at the same rate and reach the ground at the same time. If air resistance is removed all objects fall to Earth at the same rate. Children will find this concept difficult to test, as air resistance cannot be removed. They will discover that a pen and a feather will fall at different rates, as the surface area of the feather is much greater than that of the pen; the feather is therefore affected to a much greater extent by air resistance.