Forces

Holly McMahon, Laura Jones, Alex Meredith, Jayne Atkinson - Forces
By [|Laura Jones], [|Holly McMahon] and 2 others Alex Meredith Jayne Atkinson · Last edited on Friday · Edit Doc
 * Forces**


 * Forces**

Push and Pulls Forces are nearly aways Pushes and Pulls. Although they cannot be seen, the effects of them can be seen. They usually act in pairs and always act in a certain direction. They are usually measured in newtons (N) and a newton meter is used to measure. Key words related to movement - twist, spin, swing, slide, swerve, hop, jump, turn, fast, slow. There are many activities that you can do with children to illustrate this movement, the best way that the children will understand it is if they do it. For example; - ask children to draw all the pushes/pulls that they have done this morning. Here you should get answers like pushed the door, pulled the fridge and so on. - sing the song "row row row your boat..." and do the actions of pushing and pulling to row the boat. - using children's hand held toys, for example, yo-yo, cats cradle or even plastercine or blutac. These will all illsutrate the push/pull movement. - tug of war, ensure safety and demonstrate the pulling of the rope, however also the pushing down of the feet in order to pull. In order for children to understand this concept they must be able to see it, a concrete example is better. Try and get them to be using the key terms above when describing the movements that they have experienced.

Gravity Gravity acts towards the centre of the Earth. This gravitational attraction will act upon an object on or near to the Earth. Weight is the force of an object due to gravity. This can be measured in Newtons. Mass is the amount of material in an object. This is measured in grams or kilograms. A common misconception is that weight and mass are the same thing. The Earths gravity is also acting upon the Moon. This keeps the Moon in orbit of the Earth. On the Moon there is less gravitational force than on the Earth.This is because the Moon has less mass. Objects will weigh less than they do on Earth because the force of Gravity pulling them down is less. However there will be no change in the mass because the amount of material in an object has not changed. Common misconceptions of gravity are: Weight and Mass are the same thing. The moon has no gravity.

Friction
 * 1) Friction tries to stop objects sliding, or trying to slide, past each other.
 * 2) Friction will slow a moving object down.


 * The amount of friction, depends on the surface ie. the rougher the surface, the more friction there is and therefore the more an object is slowed down!**


 * Examples....**

Roads where there is lots of fast traffic: **WHY?** For road safety, so cars can stop and grip more easily

Handlebars: **WHY?** For safety – to ensure when riding a bike, the cyclist has the best possible grip

With SMOOTHER SURFACES, the amount of friction is reduced:


 * Examples...**

A sledge: **WHY?**  People on a sledge tend to WANT to glide at speed over snow. A rough surface would slow the sledge down!


 * A snowy road / wet road. **WHY?** When a rough surface gets wet, the dips and grooves in the road are filled and the rough surface is smoother.

Therefore, **FRICTION CAN BE USED FOR GREATER SAFETY!**


 * Other useful fact - Friction also produces heat.**

TEST: Get the children to rub their hands together. HOW DO WE KNOW? Get the children to rub their hands together, the children’s hands will get warmer.

Get the children to make a prediction and give a reason why. Then, get a slope (piece of wood or whatever you can find!) and get the children to try and slide different objects down it eg, boot / flip flop etc and record their results. This will highlight which kinds of surfaces increase / reduce the friction.
 * OTHER WAYS TO TEST FRICTION IN A CLASSROOM:**

This can then be developed by changing the surface tested eg. smooth / rough (school hall / playground) so that the children can physically see friction working.

Air Resistance

This is a form of friction. When objects move through the air, the air pushes against them and slows them down. It also occurs when objects are moving along the ground e.g. a car travelling along a motorway. There are two factors that affect air resistance; the size of the object (its surface area) and the speed at which the object is travelling at. The larger the surface area of an object the greater the number of air particles pushing against it and so the object will experience a greater air resistance (an open parachute as opposed to a closed parachute). The faster an object is travelling at the harder the air particles hit it and so the greater the air resistance (riding a bike and feeling the wind blowing your hair, the faster you ride the harder the wind feels).

whether an object will float or sink in air due to its weight (hot air balloons, helium balloons). Common misconception is that air is nothing because it cant be seen. You can do experiments in class using a plastic bags as parachutes to show the difference that surface area makes. Or use paper and srew into a ball and throw, compared with trying to throw a sheet of paper.
 * Air resistance must not get confused with UPTHRUST in air. Upthrust determines