Force is a wide-ranging area of primary science. Children need to develop an understanding of how forces affect both moving and static objects, the effects of gravity and magnetism and the nature of floating and sinking Specifically, they need to know that:
I . Forces can be used to describe the change in motion or shape of an object (unbalanced forces).
2 Forces can also be seen to affect a situation where no change in the shape or motion of an object is evident (balanced forces).
3 Forces can be measured in terms of direction and strength. 4 The force of friction, which restricts movement, is present in every action,
5, Gravity is a force of attraction that acts across the distance between any two bodies.
6 Forces interact in situations such as floating and sinking.
7. The forces acting over a given area can be described in terms of pressure.
8. Forces are transferred and applied by machines.
Teaching Concepts
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Concept 2: Pushing and Pushing Back
Concept 6: Floating and Sinking
Forces are pushes and pulls. Forces can make objects start or stop moving. Forces can make objects speed up or slow down. Forces can make things change direction. Forces can change the shape of objects,
Changes in the shape of objects due to forces can be either temporary or permanent, Elastic materials or objects (such as rubber bands and springs) can push or pull back against forces that are temporarily changing their shape. Gravity and magnetism are both forces that can act at a distance. Gravity is a force of attraction between a] objects, The more mass an object has, the stronger its gravitational attraction. Weight is the force that objects exert on the Earth due to gravity. The more mass an object has, the more weight it has. Materials with a lower density than water will float on water. Friction is a force that restricts movement, Friction slows down a moving object. Friction can occur between two surfaces. or between an object and the gas or liquid it moving through. Forces act in particular directions. The directions and sizes of forces can be shown using arrows on force diagrams.
Forces acting on an object are balanced when it is not moving, Forces acting on an object are balanced when it is moving but not speed or direction. Forces acting on an object are unbalanced when it is slowing down, speeding up or changing direction. The unit of force is the newton. Water pushes up on materials, making less dense materials float. This upward force of water is caned upthrust. Objects floating in water will displace a mass of water equal to that of the object. Objects sinking in water Wii! displace a volume of water equal to that of the object, Gravity causes planets to stay in stable orbits around the Sun.The gravity of the Moon causes fluctuations in the level of the sea on Earth, Friction can be reduced through the use of lubrication. Air or water resistance can be reduced by reducing the profile of the object presented to the direction of movement. Machines such as levers, pulleys and gears are used to transmit and apply forces. Machines can be used to magnify forces by applying a smaller force acting over a greater distance. Pressure is the force applied over a particular area. Applying the same force over a smaller area can increase the effect of that force on a surface.