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AQUINAS DIOCESAN GRAMMAR Solutions

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AQUINAS DIOCESAN GRAMMAR Q10. A rocket has a mass of 1000kg. (a) What is its weight on the grounds?(g = 10N/kg) W = mg = (1000)(10) = 10000N (b) At takeoff the rocket engine exerts an upward force of 15000N on the rocket. Calculate the resultant (unbalanced) force on the rocket?

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AQUINAS DIOCESAN GRAMMAR (b) At takeoff the rocket engine exerts an upward force of 15000N on the rocket. Calculate the resultant (unbalanced) force on the rocket? 10000N 15000N Resultant (unbalanced) force = = 5000 N upwards

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AQUINAS DIOCESAN GRAMMAR Q11. A railway wagon, of mass 2000kg, moving at a speed of 5m/s along a horizontal track, comes gradually to rest in a distance of 100m. Calculate the following, showing your working clearly. (a) What is its kinetic energy? K.E. = ½ mv 2 =½ (2000)(5) 2 = 25000J (b) The work done against friction while the wagon stops? Work Done against friction = Energy Changed Energy Changed(change in KE) = initial KE – Final KE = – 0 = 25000J

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AQUINAS DIOCESAN GRAMMAR (c) The magnitude of the average frictional force that stops the wagon. Work Done = Frictional Force x Distance = Frictional Force x 100 Frictional force = 100 = 250N

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AQUINAS DIOCESAN GRAMMAR Find the resultant (unbalanced) force on each of the objects below. 10N5N10N 15N10N23N Resultant Force = 5 N to the right Resultant Force = 0 N (stays at rest ) Resultant Force = 5 N to the left Resultant Force = 13 N to the left

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AQUINAS DIOCESAN GRAMMAR 10000N 15000N 5000 N upwards Find the resultant (unbalanced) force on each of the objects below N 23000N 15000N 10000N 17000N 5N 8000 N downwards 0 N stays at rest 7000 N upwards

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