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To start A meter rule, pivoted at its centre of mass, supports a 3.0N weight at its 5.0cm mark, a 2.0N weight at its 25cm mark and a weight W at its 80cm.

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Presentation on theme: "To start A meter rule, pivoted at its centre of mass, supports a 3.0N weight at its 5.0cm mark, a 2.0N weight at its 25cm mark and a weight W at its 80cm."— Presentation transcript:

1 To start A meter rule, pivoted at its centre of mass, supports a 3.0N weight at its 5.0cm mark, a 2.0N weight at its 25cm mark and a weight W at its 80cm mark. Sketch a diagram of the situation calculate the weight W

2 A LEVEL PHYSICS Year 1 Advanced Moments A* A B C
I can calculate the support force when a single support is in operation (Grade d) I can calculate force on either support when two supports are in place (Grade b) I can describe what is meant by a couple (Grade c)

3 Moment = Force x Perpendicular Distance
Determine the units for momentum

4

5 Support force is equal to the weight of the object (i. e
Support force is equal to the weight of the object (i.e. ruler) plus the weight of any object place upon it. S = W1 + W2 + Wo It is the reaction force of the object on the pivot.

6 A 30 cm ruler of 10N is balanced on a knife edge with a 0
A 30 cm ruler of 10N is balanced on a knife edge with a 0.5kg mass on the 5 cm mark and a 0.75kg mass on the 27cm mark. a) Draw a diagram b) Calculate the support (reaction) force

7 Sy Sx x y D dy dx W When there is more than one support involved to calculate the reaction force at each support you need to take moments about the other support:

8 A uniform ladder of weight 400N and length 3
A uniform ladder of weight 400N and length 3.5m is held horizontally by two people. One person supports the ladder at end A and the other supports it at point B, a distance of 1.0 m from C (the opposite end to A). Draw the set up and the three forces Calculate the supporting force provided by the person at i) A ii) B The person at A releases the ladder. Calculate the moment which the person at B must provide to keep the ladder horizontal

9 Answers B B i)120 N ii) 280 N C) 300Nm (400 x 0.75) C A 400N

10 Couples A pair of forces of equal size which act parallel to each other, but in opposite directions. This doesn’t cause a resultant linear force but does produce a turning effect. Try finding a general formula for the overall moment of the following turning forces.

11 A cyclist turns a sharp corner by applying equal but opposite forces of 25N to the ends of the handlebars. The length of the handlebars is 0.60m. Calculate the moment applied to the handlebars.

12 Exam questions worksheet

13 Next Lesson: Motion along a straight line
Lesson after that: Motion along a straight line


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