# 2.2 forces and dynamics

Head of Science at St Andrew's Cathedral School à NSW Department of Education
18 May 2011
1 sur 22

### 2.2 forces and dynamics

• 1. Topic 2 – Mechanics 2.2 – Forces and Dynamics
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• 7. F is the surface friction force acting along the surface from the point of contact .
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• 10. R is the normal reaction force of the ramp on the box acting perpendicular to the surface of contact from the point of contact .
• 11. F is the surface friction force acting along the surface from the point of contact .
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• 13. This will help identify Newton's third law paired internal forces and help solve the problem.
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• 15. Gravity is a field. The slope of that field is the gravitational field strength.
• 16. The effect of the field on an object's mass is called the object's weight due to gravity.
• 17. Weight is a force and is measured in newtons.
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• 20. M : inetial mass in kg
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• 22. G = 9.81 Nkg -1 or 9.81 ms -2
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• 24. The velocity is constant or zero
• 25. There is no change in direction.
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• 28. m : the inertial mass of the object in kg
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• 30. The acceleration will be in the same direction as the nett force.
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• 33. m = inertial mass in kg
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• 36. A 1000kg car travelling at 30ms -1 to the left.
• 37. A 50,000kg rocket travelling at 80ms -1 upwards.
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• 40. The product of force and time is called impulse and is measured in Ns
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• 42. The total impulse is found in reality by measuring the area under an F-t graph
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• 44. A cricket ball has a velocity of 130kmh -1 when bowled. The batsman applies an impulse of 350Ns to the 160g ball. What is the speed of the ball after striking?
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• 49. You can not “measure” these forces, but you can calculate them.
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• 51. Are of the same type (contact, gravitational etc)
• 52. Are of the same magnitude
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• 55. What is the magnitude of the force exerted on Box B by box A?