# Physics Forces

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• Force Basics
• Weight mass and gravity
• Gravitational Forces
• Gravity attracts all masses, you only notice it when one or more of the masses are huge aka a planet. Anything near a planet or star is attracted to it very strongly
• Two important effects:
• on the surface of a planet, it makes all things accelerate towards the ground
• Gives everything a weight
• Weight and mass= not the same
• mass is amount of stuff in object. Same value anywhere in universe
• Weight= force acting on object due to gravity (gravitational pull force on the object).
• Force is caused by gravitation fields + the size of force depends on gravitational field strength.
• Gravitational field strengths
• Varies with location, the closer you are to the mass causing the field, the stronger it is +stronger for larger masses/
• Weight of an object changes with location
• Can change depending where is  1kg on earth =9.8N, on moon =1.6N.
• Measuring Weight
• Weight is measured in newtons
• Aciting from a single point of object + centre of mass
• Centre of mass = a point at which you assume the whole mass is concentrated. For uniform object, sanme density throughout and regular shape= centre of object
• Measured using a newton meter
• Mass measure in kilograms on mass balance
• Calculatinweight
• W=mg
• Physics Forces
• Forces and their effects
• Forces and elasticity
• Investigating springs
• Past Papers
• Contact and Non-contact forces
• Vectors
• have size and direction
• e.g force, velocity, displacement,acceleration, momentum
• represented by an arrow, length shows magnitude, directions shows direction of quantity
• Scalars
• Have size
• e.g speed, distance, mass , temp. ,time
• A force is a push or pull on an object that is caused by interacting with something. All forces either contact or non contacts
• When 2 objects touch for a force to act = contact. e.g friction, air resistance, tension in rope, normal contact force
• when 2 object don't need to touch for the force to act= non-constant. e.g magnetic forces, gravitational forces, and electrostatics.
• When 2 forces interact, there is a force produced on both sides. equal and opposite (newton 3rd law)
• Resultant Forces
• if you have a number of forces acting at the same point you can replace them with a single force that has the same effect. The single force is the resultant force
• Determinin the resultant force.
• If the forces on an object, act along the same line , the resultant force is found by finding sum of all forces.
• Free body diagrams
• Work Done