Each tree has to support its mass against the downwards force of Earth's gravity. At the same time ... This topic appears in OCR, Edexcel, AQA, WJEC KS3, KS4 and GCSE in England and Wales ...

Brian Cox: Gravity is the force that keeps our feet firmly rooted to our planet. Yet although it may appear constant and unchanging, this force varies on all the planets in the solar system and on ...