General Physics 1, Lec14, By/ T.A. Eleyan

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Lecture 14 Discussion. 1. General Physics 1, Lec14, By/ T.A. Eleyan. [1] A force F = (4x ˆ i + 3y ˆ j) N acts on an object as the object moves in the x direction from the origin to x = 5.00 m. Find the work done on the object by the force.

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Lecture 14

Discussion

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General Physics 1, Lec14, By/ T.A. Eleyan

[1] A force F = (4xˆi + 3yˆj) N acts on an object as the object moves in the x direction from the origin to x = 5.00 m. Find the work done on the object by the force.

[2] A 3.00-kg object has a velocity (6.00ˆi - 2.00ˆj) m/s. (a) What is its kinetic energy at this time? (b) Find the total work done on the object if its velocity changes to (8.00ˆi + 4.00ˆj) m/s.

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General Physics 1, Lec14, By/ T.A. Eleyan

[3] A 1300 kg car drives up a 17.0 m hill. During the drive, two nonconservative forces do work on the car:

• the force of friction, and
• the force generated by the car’s engine.
• The work done by friction is –3.31  105 J;
• the work done by the engine is +6.34  105 J.
• Find the change in the car’s kinetic energy from the bottom of the hill to the top of the hill.

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General Physics 1, Lec14, By/ T.A. Eleyan

[4] A 1500-kg car accelerates uniformly from rest to a speed of 10 m/s in 3s. Find (a) the work done on the car in this time, (b) the average power delivered the engine in the first 3s, and

a)

b)

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General Physics 1, Lec14, By/ T.A. Eleyan

[5] When a 4kg mass is hung vertically on a certain light spring that obeys Hooke's law, the spring stretches 2.5cm. If the 4kg mass is removed, (a) how far will the spring stretch if a 1.5kg mass is hung on it, and (b) how much work must an external agent do to stretch the same spring 4.0 cm from its unstretched position?

a)

يحل عن طريق نسبة وتناسب

b)

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General Physics 1, Lec14, By/ T.A. Eleyan

[6] A single conservative force Fx = (2x + 4) N acts on a 5kg particle, where x is in m. As the particle moves along the x axis from x = 1 m to x = 5 m, calculate (a) the work done by this force, (b) the change in the potential energy of the particle, and (c) its kinetic energy at x = 5 m if its speed at x =1m is 3 m/s.

a)

b)

c)

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General Physics 1, Lec14, By/ T.A. Eleyan

[7] Use conservation of energy to determine the final speed of a mass of 5.0kg attached to a light cord over a massless, frictionless pulley and attached to another mass of 3.5 kg when the 5.0 kg mass has fallen (starting from rest) a distance of 2.5 m as shown in Figure

Substitute and find v

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General Physics 1, Lec14, By/ T.A. Eleyan

[8] A 5kg block is set into motion up an inclined plane as in Figure with an initial speed of 8 m/s.  The block comes to rest after travelling 3 m along the plane, as shown in the diagram.  The plane is inclined at an angle of 30' to the horizontal. (a) Determine the change in kinetic energy. (b) Determine the change in potential energy. (c) Determine the frictional force on the block. (d) What is the coefficient of kinetic friction?

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General Physics 1, Lec14, By/ T.A. Eleyan

a)

b)

c)

d)

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General Physics 1, Lec14, By/ T.A. Eleyan

[9] A block with a mass of 3 kg starts at a height h = 60 cm on a plane with an inclination angle of 30', as shown in Figure. Upon reaching the bottom of the ramp, the block slides along a horizontal surface. If the coefficient of friction on both surfaces is ,Uk = 0.20, how far will the block slide on the horizontal surface before coming to rest?

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General Physics 1, Lec14, By/ T.A. Eleyan

And find v

And find s2

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General Physics 1, Lec14, By/ T.A. Eleyan

[10] Initially sliding with a speed of 1.7 m/s, a 1.7 kg block collides with a spring and compresses it 0.35 m before coming to rest. What is the force constant of the spring?

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General Physics 1, Lec14, By/ T.A. Eleyan

[11]The ambulance (mass 3000kg) shown in the Figure(2) slides (wheels locked) down a frictionless incline that is 10 m long. It starts from rest at point A, and continues along a rough surface until it comes to a complete stop at point C. If the coefficient of kinetic friction between the ambulance and the horizontal rough surface is 0.1. (a) Calculate the speed of the ambulance at point B.(b) Compute the distance d the ambulance slides on the horizontal rough surface before stopping.

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General Physics 1, Lec14, By/ T.A. Eleyan