AQA Physics topic 5 PDF
Preview AQA Physics topic 5
2211//1111//22001177 Forces AQA Physics topic 5 2211//1111//22001177 5.1 – Forces and their Interactions 21/11/2017 Vector vs. scalar Scalar quantities have size (“magnitude”) only and no direction. Vector quantities have both size and direction. Scalar or vector??? Scalar Vector 8. Power 2. Distance 1. Mass 6. Energy 7. Time 3. Acceleration 4. Speed 9. Force 5. Velocity 21/11/2017 Vectors Here’s a man walking 10km north and then 10km east. Notice that we can replace his two movements with a “displacement vector”. Note the length and direction of this vector: 10km The same can be applied to velocity vectors: 10km 100ms-1 14.1km 5ms-1 100.1ms-1 21/11/2017 Introduction to Forces A force is a “push” or a “pull”. What forces do these pictures represent? Which of these forces would you describe as “contact forces” and which ones are “non- contact forces”? 21/11/2017 Contact or non-contact forces? Contact Non-contact 1. Friction 2. Air resistance 3. Gravitational forces 4. Tension 5. Electrostatic forces 6. Reaction 7. Magnetic forces 2211//1111//22001177 Weight vs. Mass Earth’s Gravitational Field Strength is 10N/kg. In other words, a 1kg mass is pulled downwards by a force of 10N. Weight = Mass x Gravitational Field Strength W (in N) (in kg) (in N/kg) You need to learn this equation!! M g 1) What is the weight on Earth of a book with mass 2kg? 20N 2) What is the weight on Earth of an apple with mass 100g? 1N 3) Charles weighs 700N on the Earth. What is his mass? 70kg 4) On the moon the gravitational field strength is 1.6N/kg. 112N What will Charles weigh if he stands on the moon? 21/11/2017 More information about Weight 1) How much does 1kg weigh on the Earth? 2) How much does 2kg weigh? 3) How much does 3kg weigh? 4) What are you noticing about your answers? Whatever mass goes up by, weight goes up by the same ratio. For example, if you double mass you double weight. This is called “proportionality”: 21/11/2017 Centre of Mass The centre of mass is defined as “the point at which an object’s mass is centred on”. Where is the centre of mass for these objects? 2211//1111//22001177 Resultant Force A “resultant force” is a single force that can replace all of the other forces acting on something. Calculate and draw the resultant force of the following: 700N 600N 500N 100N 50N 700N 700N 800N 800N 200N 100N
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