# Paper 2-Physics-Forces Revision MindMap

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• Created by: RYacob
• Created on: 02-06-20 11:07
• P2-Physics -Forces
• L1-Scalars and Vectors
• -to show vectors, you may be asked to draw a scale diagram     -the size (magnitude) of the vector is the LENGTH of the arrow.
• vectors:                - like displacements(distance in one particular direction) anything that we can measure in science is called a vector.              E.G. -displacement(distance in a certain direction)   -velocity (speed in a certain direction)  -acceleration   -force
• Scalars:   -if something can be measured WITHOUT a direction is called a SCALAR  E.G. -distance  -speed  -mass -temperature
• scalar quantities: have a size or magnitude, but a direction is not specified (temperature, mass, speed etc.)
• Vector quantities: have magnitude and a specific direction (velocity, acceleration etc.)
• L2-Contact and Non-Contact forces
• Contact forces: -friction -drag (air resistance) -tension -thrust
• non-contact forces: -static electricity -magnesium -gravity
• Equal forces: -forces come in pairs -when you push against a wall, you feel the wall push back
• Opposite Forces:   -when you pull on a rope, you feel the tension in the rope pull back
• Newton's Third Law: If you push or pull on something, you make a pair of forces. They are equal in size and opposite directions
• If forces are going in the same directions of an object then you ADD. If the forces are in the OPPOSITE direction, SUBTRACT them.
• L3-Work Done
• ZERO RESULTANT FORCE is the same as BALANCED FORCES
• Balanced Forces: -no change in speed or direction  -steady speed  -same direction
• unbalanced forces: -speed changes and/or direction changes
• ENERGY TRANSFERRED EQUALS WORK DONE
• "Wet Foxes Stink"  f=w/s   w=work done(j) f=force (N) s=distance(m)
• L4-HIGHER TIER-Parallelogram & Resolution Forces
• resultant force: a single force that has the effect of all forces acting on an object.
• we can use parallelograms to calculate resultant forces
• Constructing parallograms of force diagrams:(1) Open your compass to the length of the shorter line (2)Move the compass to the end of the longer line. Draw an arc with your pencil . (3) Move your compass nad open it to the length of the longer line (4) Move the compass to the end of the shorter line and draw a second arc. (5) Use the arc to construct the rest of the parallelogram. The diagnonal line in the middle will be your resultant force.
• L5-Centre of Mass and Graivity
• weight is measured in... NEWTONS. weight is measured using a ... NEWTON METRE
• CENTRE OF MASS: the weight of an object can be considered to act at a single point called 'Centre of Mass'
• for a symmetrical object the senter of mass is along the centre of symmetry
• finding the centre of mass of irregularly shaped objects: (1) suspend the object (2) Attatch a plumb line (a piece of string with a mass on the end of it). Allow the plumb line to fall to rest and draw a line down on the shape using a board pen. The centre of mass will be on this line. (3) Suspend the object from a different point and repeat the process. The centre of mass is where the lines cross.
• "Worms Munch Garbage" w=m x g     w=weight(N)  m=mass (Kg) g=gravitational field strength (N/Kg)
• L6-Extension of a Spring
• Extension of a spring: (required practical)          (1) Attach  two clamps to a clamp stand.      (2) Attach a spring to the top clamp, and a ruler to the bottom clamp  (3) Move the ruler so that its 0cm mark is level with the top  of the  spring.  (4) Measure the length of the spring.  (5) Hang a 100g mass on the spring and measure the new length of the spring. (6) Calculate the extension (stretched length -original length)  (7) Repeat until you have added a total of 500g
• Hooke's Law: f=k x e    f=force (N)       k=spring constant (N/m)               e=extension(m)   "French Kangaroos Exist"
• Hooke's law region-force is directly proportional to extension (can be seen by the straight line on graph) until the limit of proportionality(point where the line curves) at the end of the line the spring breaks.
• -When you start stretching a spring, the extension and force are proportional       -this means that every time you add 1N of force the spring stretches by the same amount.
• L7-Forces and Electricity Part 2
• Hooke's Law: LEARN force(N)=spring constant(N/m)  x  extension(m)
• Work done in stretching a spring: elastic potential enery (joules)=0.5 x spring constant (N/m) x extension squared (m)
• Elastic Potential Energy: Elastic potential energy is the energy stored in anything that is stretched or squashed. The amount of energy depends on how much the thing is stretched or squashed by, we call this the extnesion. To work out the enxtension you do: Extension=new length-original length. The extension is measured in metres. The elastic potential energy also depends on spring constant, which tells us how easy or difficult it is to stretch the thing.