let's see how quickly we can cover the required practicals for Ed Exel PS and GCSE physics you can see me and others from mansbury science carrying out some of these experiments for real over on that channel first some tips that you should always keep in mind when answering a question on a practical in your exams remember that in many of these investigations there's an independent variable the thing you change a dependent variable the other thing that changes as a result which you measure and controls variables that could change but we keep them the same throughout in order to ensure the results are accurate always say what piece of equipment you use for each measurement don't just say measure the length of the object also add with a ruler or whatever you're using that's a mark in itself State the flipping obvious if you think surely they don't want me to put that put it down anyway you never know what marks you might pick up talk about the accuracy of measurements how will you reduce errors and uncertainties for example you get your eye in line with the measurement when using a ruler or measuring cylinder to reduce Parallax error another classic thing you should put down is multiple or repeat measurements or readings to calculate a mean from finally it's okay to write your answers in bullet point format in fact I recommend it as it helps you and the examiner keep track of how many different points are being made because I'm trying to fit lows in here you might see me write abbreviated points for the sake of brevity but when you write a point do it in full make sure you use proper English don't start going all tazan like saying heat liquid with fire more like heat the water gently on a gauze on a tripod over a buns and burner flame also don't forget that you can see me and others from mansbury science doing these practicals for realsies on mans pre education link is in the description let's go physics 1 find Newton's Second Law FAL ma force equal mass time acceleration we do this by attaching slotted masses to a trolley on a track or the slider on an air track with the string going over a pulley we let the masses fall which accelerates the trolley a flag on the trolley will pass through two light Gates or photo Gates and the computer or Data Logger will calculate the acceleration there are two Alternatives we can just use one light gate to get its final velocity and use Newton's equation of motion if you have no light Gates you can just use a stop clock to get the time taken to go a certain distance using another of Newton's equations we can again get the acceleration we change the force accelerating the trolley by removing masses but these must be placed on the trolley every time why well that's because the force of gravity is not only accelerating the trolley but also the masses themselves so we must keep the total mass constant get the force by multiplying the mass by G every time plot the force against acceleration and you should once more end up with a proportional relationship a straight line going through the origin as fals ma the gradient of this line should be equal to the mass of of the trolley and masses physics two waves a few different variations here using a ripple tank you can just use light to project an image of the Waves onto a screen or piece of paper using a ruler you can measure the length of 10 waves say then divide by 10 to get the wavelength this is much easier if the oscillator making the waves is also connected to a strobe light so the waves appear stationary on the screen the signal generator that's driving the oscillator should also tell you the frequency being used if you change the frequency the wave length will change but according to the wave equation V equal F Lambda the wave speed V should remain constant that is UN unless you change the depth of the water you could also just count the number of waves reaching the end of the tank over 10 seconds if they're slow enough then divide by 10 to get the frequency waves per second the other PRACK involves getting an oscillator AKA vibration generator to produce a stationary wave on a string with masses on the end over a pulley to provide some tension we might also use a bridge instead you need to vary the frequency until you get the simplest stationary wave formed on the string one loop at this point the length of the string to the pulley or the bridge is equal to half the wavelength of the wave using this with the frequency driving the oscillator we can again calculate wave speed physics three refraction all we do is shine a ray of light from a ray box into a glass or perspect block we draw around the block Mark where the light enters and leaves join these up with a ruler and then measure the angles of incidence and refraction don't forget that every angle must be measured from the normal the line that's 90° to the surface we could use a semicircular block instead we change the angle of incidence then measure what the new angle of refraction is plotting s i against sign R will give you a straight line and the gradient of this graph gives us what we call the refractive index of the material physics 4 infrared absorption easy piece of this one just fill a lesli cube with hot water from a kettle it's got different surfaces on its four sides using an infrared detector or infrared thermometer we can detect how much heat is radiated from each side you'll find matte black is the best emitter of infrared whereas shiny silvery surfaces are the worst another PCT we can do is just have boiling tubes wrapped in different materials with a thermometer through scw a bung in the top of each have the Sun or a lamp shine on them and record their temperatures after a set time you'll find that matte black is not only the best emitter of infrared it's also the best absorber while shiny surfaces are the worst absorbers which makes sense as they reflect light well so it's also true for infrared physics five circuits now there's all sorts of little different experiments that you can do for this like resistors in series and parallel and therms and ldrs Etc but I'm just going to do the standard resistance length of wire if you want to see the other ones just watch my electricity video we just want to see the relationship between length of a wire and its resistance we use constant hand wire as its resistance doesn't change much when it gets hotter which is what we want attach the wires using crocodile clips and cables to a battery an amiter in series to measure the current and a voltmeter in parallel to measure the PD change the distance between the two crocodile Clips to change the effective length of the wire measure this with a meter rule making sure the wire is tored when you do this calculate resistance for each length by rearranging ohms law res resistance is equal to voltage PD ided by current plot resistance against length and you should end up with a directly proportional relationship that is a straight line that goes through the origin if you extrapolate the line of best fit physics six density this one often crops up in exam questions finding the density of objects or solutions to find the mass of any solid object just place it on a top pan balance if it's a regular object say a cuboid or a cylinder you can measure its Dimensions with a ruler or Veria calipers that has a higher resolution and calculate its volume from on these then use the equation mass divided by volume to find the density for any irregular object like a stone or a lumpy thing for which we can't calculate the volume we use a displacement or Eureka can fill it up with water to the spout lower the object down with string until submerged and collect the water displaced with a beaker put this into a measuring cylinder to get an accurate value for the volume of the object to calculate the density from again using the equation you can find the density of a solution by putting a measuring cylinder on a balance and zeroing then pouring in the solution allowing you to find the mass and volume pure water has a density of 1 G per cm cubed so if you find that the density of say a salt solution is 1.2 G per cm cubed that means that the concentration of the salt is 0.2 G per cm cubed physics 7 properties of water that's sa and slh we want to calculate the specific heat capacity and specific latent heat of fusion of water we heat water in a beaker with an electric heater the current and PD supplied are used to calculate the power to the heater then we mold ly that by the time and that gives us the total energy input measuring the change in temperature of the water using a thermometer or temperature probe along with the mass allows us to calculate its shc which hopefully is close to the true value of 4,200 Jew per kgam per degre C for slh we put ice in a funnel with the electric heater with a beaker underneath to catch the water produced you only start timing once the first bit of water drips down as we don't want to include the energy needed to bring the temperature up to the melting point of 0° stop timing once there is no more ice and similar to before we calculate the energy input using V * I * T divided by the mass of the ice and you have your slh a fusion of water which hopefully should be close to 334,000 Jew per kilogram the issue with both of these experiments is that the thermal energy will continually be transferred to the surroundings meaning that the measured energy input will inevitably be higher than the true value for the energy needed to raise the temperature of the water or melt the ice so you all want to think about how to reduce this Say by using insulation or a lid physics 8 Springs we can find the spring constant for a spring by fixing one end on a retor stand and a clamp and hanging slotted masses of increasing Mass to change the force on the spring that's our independent variable and measuring the extension that's our dependent variable the best way of measuring extension is to fix a ruler as close to the spring as possible with the zero Mark lined up with the bottom of the spring then just measure where the bottom of the spring goes to when it's stretched multiply the mass by gravitational field strength 9.8 every time to get the force block this against extension even though you might think the axis should be the other way around it makes it such that the gradient of the line gives you the spring constant in Newtons per meter or Newtons per centimeter if you kept your extensions in centimeters this is where hooks law fals K comes from where K is the spring constant this should be a straight line that goes through the origin showing that this is a directly proportional relationship leave a like and a comment if you found this helpful click on the card to go to the mansbury science playlist or the other card to go to the videos covering whole papers see you next time