![]() ![]() Can an object go round a curve without any force acting on it? If an object has no acceleration can you conclude there are no forces acting on it? Explain. We know now that objects in free-fall experience the same increase in speed, whatever their weights. Aristotle claimed that the speed of a falling object depends on its weight. When a junked car is crushed into a compact cube, (a) does it's mass chanage? (b) What about its weight, does that change? (a) do you think a ball will still fall back into the chimney? (b) What happens if the speed of the train increases, i.e., the train accelerates? (c) How about if the train is moving at constant speed on a circular track? If the train is moving along a straight track at constant speed. The chimney of a toy train contains a spring gun that shoots a steel ball a meter or so vertically upwards - so straight that the ball falls back into the chimney when the train is stationary. but when you jump upwards why doesn't the wall slam into you? When you stand facing the wall you are carried along at the same speed so you don't notice it. ![]() The Earth rotates once every 24 hours and so gthe western wall of your room moves in a direction towards you with a linear speed that is about 1000km/hr - the precise speed depends on your latitude. Before the time of Galileo and Newton, some scholars though that a stone dropped from the top of a tall mast on a ship moving with a constant horizontal velocity would fall vertically and hit the deck behind the mast by a distance equal to how far the ship had moved forward while the stone was falling. How can you tell which is which without opening the boxes? In an orbiting space shuttle you are handed two identical boxes, one filled with sand and the other with feathers. To gain the maximum effect you should attempt to answer them before looking at the answers! they should help you grasp the concepts underlying Newton's Laws. Try these "busters" to exercise your brain. ("I am a friend of Plato, I am a friend of Aristotle, but truth is my greater friend.") "Amicus Plato, amicus Aristoteles magis amica veritas" ![]()
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