AQA GCSE Combined Science Physics - Paper 2 SOLUTIONS GRADE A+ GUARANTEED

Vector quantities have magnitude and direction Examples of vector quantities force, velocity, momentum, acceleration 5 Sanity-Saving Tips for Arguing on the Internet Scalar quantities Only have magnitude and no direction Examples of scalar quantities speed, distance, time Vectors represented by an arrow - the length of the arrow shows the magnitude. The direction of the arrow shows the direction of the quantity A force is a push or pull on an object that is caused by it interacting with something when two objects are touching for the force to act, its a .... contact force examples of contact forces friction, air resistance, tension in ropes. etc If the objects do not need to be touching for the force to act, the force is a ...... non contact force examples of non contact forces magnetic force and gravitational force Two effects of gravity - makes all things fall towards the ground - gives everything a weight What is mass? The amount of material an object is made of It is the same value everywhere Measured using a mass balance What is weight? The force acting on an object due to gravity It depends on the strength of the gravitational field at the location of the object Measured using a calibrated spring balance - newtonmeter Equation for Weight Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg) W=mg What is weight directly proportional to? mass What are free body diagrams? Diagrams that show all the forces acting on an object What is the resultant force? The single force that replaces multiple forces acting at a single point How is work done? When a force moves an object through a distance, energy is transferred and work is done on the object Equation for 'Work Done' Work done (J) = Force (N) x Distance (m) W=Fs What is 1J equal to? 1Nm If all the forces acting on an object combine to give a resultant force of zero then the object is in ? equilibrium What could happen when you apply a force to an object? It may stretch, compress or bend What happens when an object is elastically deformed The object can go back to its original shape and length after the force has been removed What happens when an object is inelastically deformed? The object won't return to its original shape and length after the force has been removed Equation for Force 1 Force (N) = Spring Constant (N/m) x Extension (m) F=ke Extension is directly proportional to? (Hooke's Law) The force applied F∝e What is the limit of proportionality? The point at which extension is no longer directly proportional to force Practical: Investigating the link between force and extension - First, measure the original length of the spring using a milimetre ruler - Next, add different masses on the spring and measure the length of the spring in each case. - The extension = change in length - Repeat this process until you have enough measurements ( no fewer than 6) - Plot a graph with extension of the spring on the x axis and force on the y axis. - The graph will only start to curve if you exceed the limit of proportionality Equation for Elastic potential energy Elastic potential energy (J) = 1/2 x Spring Constant (N/m) x extension^2 (m) Ee = 1/2Ke^2 What is displacement? It measures the distance and direction in a straight line from an object's starting point to its finishing point What is velocity? Speed (how fast you're going) in a given direction Equation for Speed Distance Travelled (m) = Speed (m/s) x Time (s) s=vt typical speeds typical speed of a person walking 1.5m/s typical speed of a person running 3m/s Typical speed of a person cycling 6m/s what is the typical speed of a car 25m/s Typical speed of a train 55m/s Typical speed of a plane 250m/s What factors affect speed? Fitness of the person Age of the person Distance travelled Terrain Climate Gender of the person What factors affect wind speed? Temperature Atmospheric pressure Any large buildings or structures nearby e.g. forests reduce wind speed travelling through them Acceleration change in velocity in a certain amount of time Equation for Acceleration Acceleration (m/s²) = Change in Velocity (m/s) / Time (s) a=Δv/t What is deceleration? Negative acceleration - when something slows down, the change in velocity is negative What is constant acceleration? Uniform acceleration - acceleration due to gravity is uniform for objects in free fall Equation for Uniform Acceleration Final velocity² (m/s) - Initial velocity² (m/s) = 2 x Acceleration (m/s²) x Distance (m) v²-u²=2as Distance-Time Graphs - Features 1) Gradient = speed 2) Flat sections = object is stationary 3) Straight uphill sections = object is travelling at a steady speed 4) Curves = object is accelerating or decelerating 5) Steepening curve = object is speeding up 6) Levelling off curve = object is slowing down Velocity-Time Graphs - Features 1) Gradient = acceleration 2) Flat sections = object is travelling at a steady speed 3) Uphill sections = object is accelerating 4) Downhill sections = object is decelerating 5) Curves = object is changing acceleration The steeper the graph, the greater the acceleration or deceleration What does friction do? It causes objects to slow down when they rub against another surface What is drag? The resistance you get in a fluid Air resistance is a type of drag How do you reduce drag? Keep the shape of an object streamlined process of a falling object 1) When a falling object first sets off, the force of gravity is much more than the frictional force slowing it down, therefore the object accelerates 2) As the speed increases, the friction builds up 3) The acceleration is gradually reduced until eventually, the CONTINUED......