Three years ago I explained how to use photographs to estimate the speed of a passing car. You can read that article at https://physbang.com/2020/08/02/keep-the-cogs-turning/. Now it is time to use a similar technique to answer a more challenging question: what is the take-off velocity of a passenger jet? Of course, the answer could be found … Continue reading Aircraft take-off velocity
Why does hot air rise?
Easy question! It's because hot air is less dense than cold air. Except that things aren't really this simple. How does hot air know its own density and the density of the cold air that surrounds it? For that matter, how does hot air know which way is up? You might say that hot air … Continue reading Why does hot air rise?
Motion Along a Line
Having looked at the first Physics paper for this year's AQA Trilogy examination, it seems to me that a significant proportion of questions have been framed around situations and applications rather than just recalling and connecting facts. With that in mind, let's take a real-world look at motion along a line... First an important definition. … Continue reading Motion Along a Line
Resolving Vectors
Having covered the basics of resultant forces, we can progress to a method for analysing vectors that does not rely purely on scale drawings. Before proceeding, let me stress that this approach is not needed for GCSE Physics but the method should be accessible to mathematically inclined readers and will prove very useful in post-GCSE … Continue reading Resolving Vectors
Determination of ‘little-g’
One of my favourite experiments in GCSE physics is a practical that seems to have fallen from favour in recent years – but it’s still worth exploring. The experiment involves using a ticker-timer to make dots at regular time intervals (0.02 s apart) on a strip of tape that is attached to a moving object. … Continue reading Determination of ‘little-g’
Momentum
Newton's Second Law of Motion tells us that the force required to accelerate an object can be calculated by multiplying the mass of the object by the acceleration that is required (F=ma). We also know that acceleration is simply the rate of change of velocity (the change in velocity divided by the time taken for … Continue reading Momentum
Forces and Motion
Let’s get the common misconception out of the way first: moving objects do not remain in motion because there is a force that keeps them going. In fact, it’s the opposite. Moving objects always remain in the same state of motion unless an external force stops them. By “the same state of motion” we mean … Continue reading Forces and Motion
Speed and Velocity
In many situations, the word “speed” is used when in fact “velocity” would sometimes be more appropriate. Speed is the rate of change of distance: the word “rate” indicates time, so speed is simply a measure of how much the distance changes in each second of movement. If you took 80 seconds to run 400 … Continue reading Speed and Velocity
Summer Challenge
You may have better things to do during the summer vacation but, in case you find yourself getting bored, I have an investigation that you might like to tackle. The work is open to all of my students, both those of you who are still studying the GCSE course and those who have just finished … Continue reading Summer Challenge
Interpreting graphs
Graphs are a great way of presenting information in a format that is easy to understand but it's important you can describe them accurately as this skill is commonly tested in GCSE Physics papers and it ought to be an easy way to accumulate marks. I recommend a three-step approach, as outlined below. 1. Always … Continue reading Interpreting graphs