Newton's Three Laws: F = ma, Inertia and Third-Law Pairs, Worked Examples | GCSE Physics

Newton's three laws for GCSE Physics, animated, starting with the question everyone has asked: why do you lurch forwards when a bus brakes? The first law (zero resultant force means no change in velocity), a car cruising with balanced forces, and what a resultant force does: speed up, slow down or change direction. Inertia and inertial mass (Higher tier). The second law, a ∝ F and a ∝ 1/m, then F = ma worked line by line: a 1200 kg car with 3600 N of driving force and 600 N of resistance (2.5 m/s², not 3.0), a 90 N kick on a 0.45 kg football (200 m/s²), estimating a family car's force (roughly 4000 N), and inertial mass = F/a for a boat (2000 kg). The third law with two skaters pushing apart and a book on a table: which forces really are a pair, and why weight and the normal force aren't. Then circular motion and the centripetal force (Edexcel Higher), and three mistakes that cost marks. Covers: AQA 4.5.6.2.1–4.5.6.2.3 (Combined 6.5.4.2.1–3) · Edexcel 2.14, 2.15, 2.21, 2.22, 2.23 · OCR Gateway P2.2d, i, j, l, p (Combined Science and separate Physics; inertia and inertial mass Higher tier; centripetal force Edexcel Higher tier). The required practical on force, mass and acceleration is the next video. 0:00 Intro 0:08 Hook 0:34 The first law 1:20 Inertia 1:56 The second law, F = ma 2:38 Worked example: a car 3:27 Worked example: a kick 3:53 Estimating a force 4:28 Inertial mass 5:03 The third law 6:05 Moving in a circle 6:42 Common mistakes 7:02 Summary Narrated with an AI voice. Worked Example is not affiliated with or endorsed by AQA, OCR or Pearson Edexcel. Exam board names are used only to show which specifications a video covers.