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© Boardworks Ltd 2003 Force mass and acceleration

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© Boardworks Ltd 2003 Force mass and acceleration Recall and use the relation between force, mass and acceleration (including the direction). Describe, qualitatively, motion in a curved path due to a perpendicular force.

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© Boardworks Ltd 2003 How are mass, force and acceleration related? Two masses of 1 kg and 4 kg are both subject to the same force, which one will accelerate the fastest? The lower the mass, the greater the acceleration for a specific force. This is why Grand Prix cars get faster as they use up their fuel. Less fuel, means less mass, less mass means greater acceleration.

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© Boardworks Ltd 2003 F=ma We can express the relationship between force, mass and acceleration using the equation: Force = mass x acceleration F =ma Force measured in Newtons (N) Mass measured in kilograms (kg) Acceleration measured in metres per second per second (ms -2 )

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© Boardworks Ltd 2003 Formula triangles F m aa x Formula triangles help you to rearrange formula. The triangle for the f=ma formula is shown below: Whatever quantity you are trying to find, cover it up and it will leave you with the calculation required. So if you were trying to find mass, m….. …you would cover m up… …and you are left with the sum… m = F a

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© Boardworks Ltd 2003 Force calculations: 1.What force will make a mass of 4 kg accelerate at 5 ms -2 ? 2.A force of 50N acts on a 2 kg mass. What will be the acceleration of the mass? 3.A force of 2 000N accelerates a car at 2.5 ms -2. What is the mass of the car? Force = 20 N Acceleration = 25 ms -2 Mass = 800 kg

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© Boardworks Ltd 2003 Force questions: 1.Label the forces acting upon a moving bike. 2.Fill in the table: A > (C+D)A =(C+D) A < (C+D) Bike accelerating Bike at steady speed Bike decelerating A B C D E A - Thrust B - Reaction C – Air resistance D - Friction E - Gravity

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© Boardworks Ltd 2003 Moving in circles Watch the bucket demonstration Draw a force diagram of: The bucket The water

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© Boardworks Ltd 2003 Questions (Assuming the bucket travels at a constant speed) What is the change in speed? What is the change in velocity? What is the definition of velocity? What is the definition of acceleration? Is the bucket accelerating?

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© Boardworks Ltd 2003 Applet http://phet.colorado.edu/en/simulation/ motion-2dhttp://phet.colorado.edu/en/simulation/ motion-2d

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© Boardworks Ltd 2003 Notes F=ma (acceleration is always in the direction of the force) Any change in velocity is an acceleration……. …… including changes in direction. An object moving in a circle at constant speed is accelerating.

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