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Rope bridge

Rope bridge. Rope Bridge Gravity. Episode 3: Gravity. Objectives:. To explore the force of gravity and calculate the weight of a variety of objects. To consider the weight of the bridge platform. Rope Bridge Gravity. 2. Engage. Rope Bridge Gravity.

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Rope bridge

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  1. Rope bridge Rope BridgeGravity Episode 3: Gravity

  2. Objectives: • To explore the force of gravity and calculate the weight of a variety of objects. • To consider the weight of the bridge platform Rope BridgeGravity 2

  3. Engage Rope BridgeGravity Link: http://www.youtube.com/watch?v=8DPP3Ei9X_0 Hello again! I have a video clip to show you - the person who took it said this was probably the most dangerous rope bridge in the world! 3

  4. Engage Rope BridgeGravity So! Not a nice bridge to cross! What made it dangerous? It was too long? Or too high? Or...what do you think? Why do you think the builders of the bridge would make it that way? 4

  5. Engage The lack of slats on the pathway does save building materials and reduce the weight of the bridge. But what do we mean by weight? Rope BridgeGravity 5

  6. Weight is a force. If we think about the bridge the weight of the person in the middle pushes down on the bridge platform. The force the person applies to the bridge is called their weight. Explore Weight pushes downwards Rope BridgeGravity Bridge pushes upwards 6

  7. Explore Rope BridgeGravity Gravity is a force which acts between masses. Gravity pulls the person and the Earth closer together. Because the Earth is so big it moves very little but the person is small so they can move more easily. We can detect this force pulling the object towards the Earth as weight. 7

  8. Explore We can calculate the weight of an object with this formula: Weight = mass × acceleration of the gravityW = m × g. g is the acceleration due to gravity. It is a measure how hard gravity pulls the person and the Earth together. g is the same for all objects all over the Earth. It can be measured at 9.8m/s2. Since weight is a force it is measured in newtons. Rope BridgeGravity 8

  9. So weight is different from mass? Explore Yes. Mass is how much stuff is present in an object and is measured in grammes or kilograms. And its measured with a ‘weighing machine’? Rope BridgeGravity Yes! That is a bit confusing. Weight should really be measured with a spring balance. The unit for weight is really newtons - the unit for force. Hmmmm .... I think I understand! SS1 9

  10. Explore I think you’re getting the idea. Why not check your spring balances and weighing machines work properly. Find out the weights and masses of these objects using both methods and see if they agree. Rope BridgeGravity 10

  11. Explain How did your experiments go? How close were the results from the two methods? Rope BridgeGravity 11

  12. Elaborate OK, so we know that the weight of traffic can damage a bridge and that the pathway can be quite heavy. Calculate the weight of the pathways on these bridges. Rope BridgeGravity 12

  13. Elaborate 23 m Rope BridgeGravity Wooden slats are 10 cm wide and spaced 10 cm apart. Each wooden slat weighs 4.5 kg 13

  14. Elaborate 23 m Rope BridgeGravity Wooden slats are 12 cm wide and spaced 5 cm apart. Each wooden slat weighs 5 kg. 14

  15. Evaluate Rope BridgeGravity This bridge is similar to the one that will replace the damaged one. It is 27.5 m long and has 20cm wide wooden slats placed with a 2 cm gap between them. Each slat has a mass of 8kg. The support rope is made of steel and can carry 25 000 N. 15

  16. Evaluate Rope BridgeGravity If 60 people cross the bridge at the same time in the morning to go to work what would be the total weight the cables would have to support? Would the bridge be safe? 16

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