How To Do Any GCSE Physics Calculation Exam Pro Tip

one of the reasons prefer physics over the other Sciences is because you don't need to remember huge amount of fact it's all about how you apply just little bit of knowledge so when it comes to calculation questions in your exams well everything's already there you don't really have to remember anything so in theory you should get all of those marks but sometimes it's little bit tricky to remember how to do calculations properly so let me teach you so here's the question we're going to use 50 gram ball drops from rest and it falls eight meters to the ground at what speed does it hit the ground first thing we do number one we write down the data we've been given in the question so what have we been told we've been told the mass of the ball is 50 grams and we've been told the height that it falls eight meters but also write down what we're being asked to find we're being asked to find the speed what's the symbol for Speed well it's because it's basically velocity so we're going to put question mark there for that and that's very important because that makes the next step lot easier you might have to infer some information as well what would mean by that well sometimes the question might have number in it but it doesn't actually tell you the number for example here we're told that the object falls from rest what does that mean that means that the speed of the object is zero to begin with and it's good idea to convert units to whenever you do calculations it's only meters amps or volts it's not kilovolts it's not kilometers that go into calculation just remember that the only exception to that is kilograms kilograms is what goes into calculation not grams and so that means we must convert this into kilograms foreign remember if you're going to bigger unit then you need to divide by the conversion factor so we divide by thousand here we know we want fewer kilograms than grams step two figure out what the question is about is it about forces or energy or electricity it could be more than one of these here we're talking about something that starts off high and force and you should know that that therefore is about energy what do we know about energy energy is always conserved and that should help us in the next bit then step three find the equation with these variables in now this is the great thing is that you'll be given formula sheet so you don't even have to remember the equations and you're given them in symbol form so always say that it's worth writing them down in simple form we've already used symbols up here anyway sometimes it might have to be two equations not one so just be careful there and that is true in this case we don't have an equation that has and in but because we figured out the question is to do with energy well we know that we're going to have to use our equation for gravitational potential energy and kinetic energy so I'm going to say EP for potential energy and EK for kinetic energy and that's equal to half times the mass times squared half MB squared now in any question to do with things falling you'll always be told what they want to be gravitational field strength more often than not they'll say that it's just 10 or if not they'll just say 10 but it might be 9.8 as well but you'll always be told that we've written our equations down it's really important that you do that and now we need to figure out do we need to rearrange these well what do we have we have we have we have and we're trying to find so we can't really use kinetic energy equation yet can we but let's figure out what the gpe is so gpe or I've just written EP for sure it's really important then that you write the equation with the numbers in so 0.05 times 10 times eight now don't be lazy and skip this step it's important that you write down what calculation you're actually doing because if you get the answer wrong at the end then you'll miss out on marks for workings and popping that into my calculator that gives us gravitational potential energy of four joules great we now have our gpe and we know that if something Falls then its gpe is turned into ke so that means that if it had four joules of GPU at the top it now has four joules of at the bottom so now we need to rearrange this equation Now with an equation with three things in you can just do an equation triangle and they're okay but see if you can get used to rearranging equations properly what do we want to make the subject we want to make the subject and the trick is to move things from one side of an equation to the other we do the opposite with them so I'm going to write it out again but I'm just going to drop the there so is equal to half MV squared they're all multiplied aren't they let's get rid of the half first well to get rid of times half we need to divide by half or is that the same as that's the same as multiplying by two there we go two times the energy equals MV squared and then we need to get rid of the to the other side as well let me write it out again I'm just going to say 2E 2 times the energy is equal to MB squared so get rid of the times we divide by it on the other side we do the opposite we're not quite done because we just want we don't want squared so to undo this we square root the whole thing now you can write down the equation now the final step write down the calculation and punch it into your calculator so we can write down is equal to the square root of 2 times the energy what was that four joules divided by the mass 0.05 that gives me an answer of 12 point well six four nine one but we should round the rule of thumb is three significant figures so in this case this would just be 12.6 so we're just going to round it to that you couldn't say replace the symbols in the equation with numbers and then rearrange and you'll end up with the same answer but doing it this way is better you might see there is shortcut in this question but I've gone around the house is to show you how to do it properly I've also done video specifically on how to do any electricity calculation check it out leave like if this has been helpful and I'll see you in the next video