Physics explained: every letsBug physics post

Forces, motion and GPS explained with real numbers, from rockets to running tracks. Each post goes with a letsBug video and ends with practice questions.

1. 10 Newton's second law examples in everyday life (F = ma): 10 Newton's second law examples in everyday life, from trolleys and lifts to cricket catches and rockets, each worked out with F = ma and numbers.
2. How Do Rockets Work in Space With No Air? Newton's Third Law: Rockets push their own exhaust gas, and the gas pushes back. Newton's third law explained with a real Falcon 9 example, plus the classic mix-up.
3. Distance vs displacement: how can displacement be zero?: Distance vs displacement, speed vs velocity: why a 400 m lap has zero displacement, with worked examples, m/s conversions and exam questions.
4. How to read distance-time and velocity-time graphs: How to read distance-time and velocity-time graphs: read the axis first, then use the gradient or the area. Why a flat line isn't always stopped.
5. Which SUVAT equation to use? The 3 equations of motion: Which SUVAT equation to use: list s, u, v, a, t and pick the one without the letter you don't need. Plus why braking is a negative acceleration.
6. What is a resultant force? Constant velocity means zero: A resultant force is all the forces on an object added into one. See why it's zero for a car at a steady 100 km/h, and how mass differs from weight.
7. What is momentum? Conservation of momentum and recoil: Momentum is mass times velocity, p = mv. See why a cricket ball can have more momentum than a bowling ball, and how recoil works.
8. What is work in physics? Carrying a bag does no work on it: Work done is force times distance in the force's direction. See why carrying a bag does no work on it, and what power and kWh really mean.
9. How Does GPS Work Without Internet? It's All About Time: How GPS works without internet: your phone just listens to satellite clocks. How to use it offline, why 4 satellites, and why it needs Einstein.

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