Forces

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• Forces
• Vectors and Scalars
• Vector quantities have magnitude and specific direction but scalar quantities have magnitude and no direction
• Vectors are force, velocity, displacement, acceleration, momentum
• Scalars are speed,distance, mass, temp, time etc.
• Contact and Non-Contact Forces
• Contact forces need objects to be touching for a force to act e.g. friction and tension on ropes
• Non-contact don't need the objects to touch for force to act e.g. electrostatic force
• Resultant forces is the overall force on an object
• Newton's third law: When 2 objects interact they exert equal an opposite forces on each other
• Work Done
• Means energy transferred and calculated by force(N) x distance(m). Work done is measured in J. If a resultant force moves an object, work is done
• Parallelogram and Resolution of Forces
• Draw all the forces acting on object to scale and tip to tail. Resultant force is the line between 1st and 2nd force. Find magnitude and direction by measuring length and angle.
• Gravity and Centre of Mass
• Centre of mass is where the weight of an object can be considered to act at a single point
• Weight is the force acting on earth due to gravity. Weight of an object depends on the GFS at the point where the object is. Weight and Mass are directly proportional
• Mass is how heavy an object is. Weight is calculated by mass(kg) x gravatational field strength(N/kg).Weight is measured in Newtons
• Extension of a Spring- REQUIRED PRACTICAL
• Steps:Attach 2 clamps to a clamp stand, attach a spring to the top clamp and a ruler to the bottom one, measure original length of spring, hang a 100g mass and measure new length, calculate extension(streched - original), repeat until you hang a total of 500g
• Forces and Elasticity
• If an object is elastically deformed, it can go back to its original length and length after force is removed and ALL the energy is transferred to it's EPE store if the force stretches or compresses the object.
• Hooke's Law: F(N) = k(N/m) x e(m)
• Work Done in Stretching a Spring: EPE(J) = 0.5 x spring constant(N/m) x (extension)>2
• Spring constant is a measure of the stiffness of a spring up to its limit of proportionality or elastic limit. And extension and force are directly proportional.