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Transcript

Note 2 Force and Motion This class is all about the relationship between force and motion. Experiment 1 Drop an object from a height. Conclusion 1 Force makes objects move. This is also how we define force operationally. Experiment 2 How does the object moves? Conclusion 2 Force accelerates objects. Experiment 3 Place the object on a table. Conclusion 3 Only the net force accelerates objects. page 1 Experiment 4 Change the net force on the object without changing the mass of the object. Here is the cart pulled by a certain weight. Here is the cart pulled by a twice the weight. Conclusion 4 The larger the net force, the larger the acceleration. The net force on the object is measured to be proportional to the acceleration of the object. ΣF ∝ a or ΣF = constant for m constant a page 2 Experiment 5 Change the mass of the object without changing the net force on the object. Conclusion 5 The larger the mass, the smaller the acceleration. The mass of the object is measured to be inversely proportional to the acceleration of the object. m∝ 1 or ma = constant for ΣF constant a Experiment 6 Can we find any other parameters that matter? Conclusion 6 No. The final conclusion here is that the acceleration of an object is produced by the net force moderated by the mass of the object. a= ΣF m This is Newton’s second law of motion. The forces and the net force and the acceleration are all vectors. It is usually written this way. ! ! ΣF = ma page 3