# Forces

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• FORCES
• gravity
• All objects have a force that attracts them towards each other. This is called gravity
• Gravitational force increases when
• the objects are closer
• the masses are bigger
• Gravity is a force that un-noticably pulls you down (to the centre of the earth)
• The Moon's gravity is one sixth of the Earth's gravity
• wieght
• Weight is a force caused by gravity
• The more mass the object has the greater its weight will be
• Weight is measured in newtons
• On the surface of the Earth an object with a mass of 1 kg has a weight of about 10 N
• mass
• The mass of an object is the amount of matter
• The more matter an object contains, the greater its mass
• Mass is measured in kilograms, kg, or grams, g
• push
• pull
• NOTE
• Remember that mass is measured in kilograms, kg, and weight is measured in newtons, N
• The weight of an object changes if the strength of gravity changes
• Pressure
• Equation - pressure = force ÷ area = ...nm2/pa
• Frictional Forces
• friction between tyres and the road stop cars from skidding
• friction between the brakes and wheel help bikes and cars slow down
• friction between our shoes and the floor stop us from slipping
• air resistance
• air resistance is caused by air against the fast moving object
• The faster the vehicle moves, the bigger the air resistance becomes
• Streamlined
• Streamling in where an object is specifically shaped to let the air flow past/over the object