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Part 3 /3 High School by SSL Technologies

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Physics Ex-38 Question-1 A force of 12 N, acting 60 o from the horizontal, is applied to a 20 kg cart initially at rest resulting in a final velocity of 10 m/s. If the force of friction is 2 N, answer the following questions concerning the cart in going from point-A to point-B (a distance of 250 m). Click Was the cart at rest? a) No What was the applied force? b) 12 N [E 60 o N] What was the horizontal component of the applied force? c) 6 N right What was the frictional force? d) 2 N left Click What was the resultant force? e) 4 N right Click (While traveling from point-A to point-B) (F R = F A – f = 6 N – 2 N = 4 N) s = 250 m v i = 0v f = 10 m/s 20 kg f = 2 N A B F A = 12 N 60 o F H = 6 N “velocity not constant”

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Physics Ex-38 Question-1 A force of 12 N, acting 60 o from the horizontal, is applied to a 20 kg cart initially at rest resulting in a final velocity of 10 m/s. If the force of friction is 2 N, answer the following questions concerning the cart in going from point-A to point-B (a distance of 250 m). Click s = 250 m v i = 0v f = 10 m/s 20 kg f = 2 N A B F A = 12 N 60 o F H = 6 N What was the acceleration of the cart? f) 0.2 m/s 2 What was the initial E K of the cart? g) 0 What was the final E K of the cart? h) 1 000 J How much work was done on the cart? i) 1000 J What becomes of the work done on the cart? j) It is transferred to the cart in the form of E K (faster speed). Click

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Physics Ex-38 Question-1 A force of 12 N, acting 60 o from the horizontal, is applied to a 20 kg cart initially at rest resulting in a final velocity of 10 m/s. If the force of friction is 2 N, answer the following questions concerning the cart in going from point-A to point-B (a distance of 250 m). Click s = 250 m v i = 0v f = 10 m/s 20 kg f = 2 N A B F A = 12 N 60 o F H = 6 N How much work was done to overcome friction? k) 500 J What was the total work done? l) 1500 J Click Summarize the amounts of work done: n) 1) To accelerate the cart 1000 J 2) To raise the cart 0 3) To overcome friction 500 J 4) Total work done 1500 J (Cart was not raised) Remember that the force must be parallel to the distance in the Work Formula. (1500 J – 500 J) Click

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Physics Ex-38 Question-2 A force of 110 N, acting 60 o from the horizontal, is applied to a 10 kg cart whose initial velocity is 4 m/s. The final velocity is 16 m/s. If the frictional force of 5 N, answer the following questions concerning the cart in going from point-A to point-B (a distance of 24 m). Click Was the cart at rest? a) No What was the applied force? b) 110 N [E 60 o N] What was the horizontal component of the applied force? c) 55 N right What was the frictional force? d) 5 N left Click What was the resultant force? e) 50 N right Click (While traveling from point-A to point-B) (F R = F A – f = 55 N – 5 N = 50 N) s = 24 m v i = 4 m/sv f = 16 m/s 10 kg f = 5 N A B F A = 110 N 60 o F H = 55 N “velocity not constant” Click

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Physics Ex-38 Question-2 A force of 110 N, acting 60 o from the horizontal, is applied to a 10 kg cart whose initial velocity is 4 m/s. The final velocity is 16 m/s. If the frictional force of 5 N, answer the following questions concerning the cart in going from point-A to point-B (a distance of 24 m). s = 24 m v i = 4 m/sv f = 16 m/s 10 kg f = 5 N A B F A = 110 N 60 o F H = 55 N Click What was the acceleration of the cart? f) 5 m/s 2 What was the initial E K of the cart? g) 80 J What was the final E K of the cart? h) 1 280 J How much work was done on the cart? i) 1 200 J Click Work done on cart = total energy – energy lost to friction 1280 J – 80 J = 1200 J

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Physics Ex-38 Question-2 A force of 110 N, acting 60 o from the horizontal, is applied to a 10 kg cart whose initial velocity is 4 m/s. The final velocity is 16 m/s. If the frictional force of 5 N, answer the following questions concerning the cart in going from point-A to point-B (a distance of 24 m). s = 24 m v i = 4 m/sv f = 16 m/s 10 kg f = 5 N A B F A = 110 N 60 o F H = 55 N Click How much work was done to overcome friction? j) 120 J What was the total work done? k) 1320 J Summarize the amounts of work done: l) 1) To accelerate the cart 1200 J 2) To raise the cart 0 3) To overcome friction 120 J 4) Total work done 1320 J (Cart was not raised) (1320 J – 120 J) Click

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Physics Ex-38 Question-3 A 10 kg cart is traveling at 12 m/s towards the right. If a frictional force of 40 N stops the cart in a distance of 18 m, answer the following questions concerning the cart in going from point-A to point-B. Click Was the cart at rest? a) No What was the frictional force? b) 40 N left (or – 40 N) What was the resultant force? c) 40 N left (or - 40 N) What was the acceleration? d) - 4 m/s 2 Click (While traveling from point-A to point-B) s = 18 m v i = 12 m/s v f = 0 10 kg f = 40 N A B “velocity not constant” Click

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Physics Ex-38 Question-3 A 10 kg cart is traveling at 12 m/s towards the right. If a frictional force of 40 N stops the cart in a distance of 18 m, answer the following questions concerning the cart in going from point-A to point-B. Click What was the initial E K of the cart? e) 720 J What was the final E K of the cart? f) 0 How much energy did the cart lose? g) 720 J What becomes of the energy lost by the cart? h) Click s = 18 m v i = 12 m/s v f = 0 10 kg f = 40 N A B Used to overcome friction (lost as heat and sound)

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Physics Ex-38 Question-4 A hammer falls from a scaffold and 1.5 s later strikes the ground with a kinetic energy of 157.5 J. What is the weight of the hammer? Click

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Physics Ex-38 Question-5 A projectile, whose mass is 800 g, is shot into the air with a velocity of 25 m/s, 42 o N of E. Determine the kinetic energy of the projectile one second after it is fired. Click

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Physics Ex-38 Question-6 Starting from rest, a car reaches a velocity of 60 m/s in a distance of 120 m. Assuming the system is frictionless and knowing that the motor of the car produces a force of 3 x 10 4 N, calculate the mass of the car. Click

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Physics Ex-38 Question-7 The mass of an electron is 1.67 x 10 27 kg. What work must be done on the electron in order to give it a speed of 2.5 x 10 7 m/s? Click

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Physics Ex-38 Question-8 A bullet of mass 2 g, traveling at 500 m/s, is fired at a piece of wood. The bullet emerges from the wood with a speed of 100 m/s. If the retarding force of friction was 4800 N, calculate the thickness of the piece of wood. ? Click

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Physics Ex-38 Question-9 Click What is the mass of a stone that is thrown in the air with a velocity of 1.1 m/s and with an initial kinetic energy of 0.0121 J? Click

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Physics Ex-38 Question-10 Two vehicles, X and Y, are traveling at the same speed. Vehicle-X has twice the kinetic energy of vehicle-Y. What is the value of the following ratio? Click Mass of vehicle-X Mass of vehicle-Y

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