E11. A 5-kg rock is going to be moved either vertically or horizontally. a. What is the increase in the potential energy

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E11 A 5 Kg Rock Is Going To Be Moved Either Vertically Or Horizontally A What Is The Increase In The Potential Energy 1 (57.95 KiB) Viewed 35 times

E11. A 5-kg rock is going to be moved either vertically or horizontally. a. What is the increase in the potential energy of the rock when lifting it to a height of 1.8 m without acceleration? b. What is the increase in kinetic energy to accelerate the same rock horizontally from rest to a speed of 6 m/s? c. Which requires more work: lifting the rock 1.8 m or ac- celerating it horizontally to a speed of 6 m/s? E12. At the low point in its swing, a pendulum bob with a mass of 0.15 kg has a velocity of 3 m/s. a. What is its kinetic energy at the low point? b. What is its kinetic energy at the high point? c. What is its potential energy at the high point (assuming the potential energy at the low point was zero)? d. Ignoring air resistance, how high will the bob swing above the low point before reversing direction? E13. A 0.40-kg mass attached to a spring is pulled back horizon- tally across a table, so that the potential energy of the sys- tem is increased from zero to 150 J. Ignoring friction, what is the kinetic energy of the system after the mass is released and has moved to a point where the potential energy has decreased to 60 J? E14. A sled and rider with a combined mass of 70 kg are at the top of a hill that rises 9 m above the level ground below. The sled is given a push, providing an initial kinetic energy at the top of the hill of 1200 J. a. Choosing a reference level at the bottom of the hill, what is the potential energy of the sled and rider at the top of the hill? b. After the push, what is the total mechanical energy of the sled and rider at the top of the hill? c. If friction can be ignored, what will be the kinetic energy of the sled and rider at the bottom of the hill? E15. A roller-coaster car has a potential energy of 400,000 J (400 kJ) and a kinetic energy of 130,000 J (130 kJ) at point A in its travel. At the low point of the ride, the po- tential energy is zero, and 60,000 J (60 kJ) of work has been done against friction since it left point A. What is the kinetic energy of the roller coaster at this low point (in kJ)?