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### 00 - M1 Facts to memorise

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 Term Definition What is a Vector? Must have MAGNITUDE and DIRECTION What is a Scalar? Has only MAGNITUDE On a distance/time graph, what does the gradient tell you? speed On a speed/time graph, what does the gradient tell you? acceleration On a speed/time graph what does the area under the graph tell you? Distance covered What is velocity? VectorDistance in a given direction/time taken What is speed? Scalardistance/time What is average speed? Scalartotal distance/total time What is average velocity? Vectordisplacement/total time taken What are the 5 equations of motion? v=u+at v2=u2+2as s=ut+at2/2 s=vt-at2/2 s=(u+v)t/2 What is the condition for using the 5 equations of motion? acceleration must be constant What is distance? The total length that has been moved. What is displacement? The direct distance between start and end points What does negative acceleration mean? slowing down What is negative displacement? displacement in the opposite direction What is acceleration due to gravity? 9.8 m/s2ALWAYS acts downwards A particle is thrown vertically upwards. What is its velocity at its highest point? zero What does equilibrium of forces mean? horizontal forces add up to zerovertical forces add up to zero Is a force a vector or a scalar? vector How do you find the magnitude of the resultant of 2 perpendicular forces? Pythagoras How do you find the magnitude of the resultant of several non perpendicular forces Find perpendicular components (ie i,j) of all forces and then use pythagoras. How do you find the angle at which a force is acting if you know its i and j components? tan What is an i vector a unit vector acting horizontally to the right What is a unit vector a vector that has a magnitude (ie a length) equal to 1 What is a j vector? A unit vector acting vertically upwards How do you find the magnitude of a vector given in the form ai + bj? Pythagoras√(a2+b2) How do you find the direction of a vector given in the form ai + bj? tanθ=b/a Give 3 facts about the vector A and the vector -A They have equal magnitudesThey are parallelThey point in opposite directions Give 3 facts about the vectors A and B if A=B They are equal in magnitudesThey are parallelThey point in the same direction Give 3 facts about the vectors A and 2A One is twice as long as the otherThey are parallelThey point in the same direction When using the formula F=ma, what does the F stand for F is the resultant of all the forces acting upon a particle When 2 particles are connected, how do you find their acceleration? F=ma for the whole system, taking the direction of movement as positive. When 2 particles are connected, how do you find the tension in the string joining them? F=ma for one particle.If possible, use the particle which has +T acting upon it. How many diagrams must you draw when answering a question? Draw a new diagram each time the information about the question changes. What is the formula for the maximimum friction (fmax)? fmax=μR In which direction does friction always act? Friction always opposes motion, so it will always act in the opposite direction to the one the particle is moving in. If the pushing force is less than the maximum frictional force, what happens? Nothing.The system is stationary, v=0f=pushing force, so equilibrium is maintained If the pushing force is equal to the maximum frictional force, what happens? Nothing.The system is at its limit.fmax=pushing force, so equilibrium is maintained.Although often v=0, it is possible for v to be present, but it will be constant. If the pushing force is greater than the maximum frictional force, what happens? There is an imbalance of forces, so the particle accelerates When a body is said to be 'on the point of slipping', what does this mean The system is at the limitfmax=pushing forcev is constant (often = 0) What is a 'moment'? The 'turning effect' which is dependent on the magnitude of the force and the distance the force is from the pivot.Moment = force x distance In a friction question, what does equilibrium mean? The pushing force is less than or equal to fmax In a moments question, what does equilibrium mean? All clockwise moments = all anticlockwise moments OR The sum of all the moments = 0 What is momentum The effect of a moving mass momentum = mass x velocity What is conservation of momentum total momentum before = total momentum after Remember to draw before and after diagrams What are the units of momentum? Ns What is impulse? Impulse = change of momentumImpulse = mv - mu ALSO Momentum = Ft I = Ft = mv - mu What are the units of impulse? Impulse is a change of momentum, so its units are the same as momentum, ie Ns