Mass and Gravitational Potential Energy

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Work done by a constant force
1- The drawing shows a plane diving toward the ground and then climbing back upward. During each of these motions, the lift force acts perpendicular to the displacement , which has the same magnitude, 1.7 × 103 m, in each case. The engines of the plane exert a thrust , which points in the direction of the displacement and has the same magnitude during the dive and the climb. The weight of the plane has a magnitude of 5.9 × 104 N. In both motions, net work is performed due to the combined action of the forces , and .

a. Is more net work done during the dive or the climb? Explain.
b. Find the difference between the net work done during the dive and the climb.
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The coefficient of kinetic friction, µk , between the bike tires and the road.

13- The figure below depicts the motion of a mass m = 300 kg as it slides along a track, which has one smooth segment and two rough segments of kinetic friction coefficient of 0.4. If the mass was released from rest at point A on the track,

a. Find the point where the KE of the mass is zero (i.e. point E where the mass comes to a complete stop)
b. Plot (draw) the kinetic energy of the 300 kg mass as a function of position from point A until point D. [Show all work, use proper scale, show equations and substitution with units and show all points on the graph].

14- The ambulance shown in the figure below (3000 kg) slides down a frictionless incline that is 10m long. It starts from rest at point A. Then it continues along a rough surface (BC) until it comes to a complete stop at point C.

a. Calculate its speed at point B
b. If the coefficient of kinetic friction of the rough segment (BC) is 0.1, calculate the distance d the ambulance slides on before stopping.

15- Bicyclists in the Tour de France do enormous amounts of work during a race. For example, the average power per kilogram generated by Lance Armstrong (m = 75.0 kg) is 6.50 W per kilogram of his body mass.
a. How much work does he do during a 135-km race in which his average speed is 12.0 m/s?
b. Often, the work done is expressed in nutritional Calories rather than in joules. Express the

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