Before you read this post, I suggest you read posts 16.13, 16.16, 16.17, 16.19 and 16.20. Most people know that “energy” has a precise meaning in science, for example when applied to nutrition or in the phrase “renewable energy”; unfortunately, several people who I’ve met completely misunderstand what this meaning is. Energy is simply the… Continue reading 16.21 Energy

I suggest that you read post 16.13, post 16.16, post 17 and post 16.19 before you read this one. A force does work when it moves something. If a constant force pushes or pulls something in the direction in which it pushes or pulls, the work that it does is defined to be the value… Continue reading 16.20 Work

16.19 Why do things stop moving if we don’t push or pull them? I suggest that you read posts 16.2, 16.4, 16.12 and 16.13 before this. According to Newton’s second law (post 16.2), an object will keep on moving for ever unless we do something to stop it. To make a moving object slow down… Continue reading 16.19 Why do things stop moving if we don’t push or pull them?

If you are reading this, you must be alive; the device you are reading it on (computer, tablet, phone) is not alive. The science of living things is a specialised subject called biology. You might then expect that we can define what makes something alive. Usually living things are defined to have several characteristics which… Continue reading 16.18 What is life?

Before you read this, I suggest that you read posts 16.13 and 16.16. In science the weight of an object is the force exerted on it by a gravitational field (post 16.16). We measure mass in kilogrammes (post 16.13) and weight in newtons (post 16.13) because it is a force. In everyday English we say… Continue reading 16.17 Weight

Before you read this, I suggest you read posts 16.12 and 16.13. When we push or pull something we change its motion by exerting a force on it (post 16.13). Now suppose I’m holding an object. The object is not moving (in my frame of reference). But if I stop holding the object, it drops.… Continue reading 16.16 Gravity

I’ve met a lot of people who don’t try to understand scientific ideas because they are “too difficult” or “boring”. But if you’ve been following this blog so far, I hope that you agree that there is nothing difficult about the ideas I’ve used so far. It is possible to explain them in simple English.… Continue reading 16.15: Science education

Have you ever noticed that car wheels sometimes go the wrong way round in movies and on television? When a car is moving forwards, the wheels go round in a clockwise direction. But sometimes they seem to go the other way round. This effect occurs because moving pictures consist of a sequence of still pictures… Continue reading 16.14 Aliasing – why car wheels can go the wrong way round in movies

I suggest that you read posts 16.2, 16.4 and 16.12 before this. We have seen that an object won’t change its velocity unless it is pushed or pulled in some way (post 16.2). Here we will think about what happens when its velocity does change. To keep things simple, we’ll think about an object moving… Continue reading 16.13 Changes in movement

I suggest that you read posts 16.2 and 16.4 before this. Remember that whether or not something is moving depends on the state of motion of the observer (Post 16.4). So, when we measure movement, we measure it compared to the movement of an observer. Providing the observer is not changing speed or direction, this… Continue reading 16.12 Measuring movement