Hello, I need help with 71-76

al force of the Sun on Earth be positive, negative, or zero over the next 6 73. If a 0.5-kg ball is dropped from a height of 6 m, what is its months? Over the next year? kinetic energy when it hits the ground? 68. How much work is performed by the gravitational force 74. A 2-kg block is released from rest at the top of a 20-m- on a satellite in near-Earth orbit during one revolution? long frictionless ramp that is 4 m high. At the same time, an identical block is released next to the ramp so that it 69. How much work does a 55-kg person do against gravity in drops straight down the same 4 m. What are the values walking up a trail that gains 720 m in elevation? for each of the following for the blocks just before they 70. A woman with a mass of 65 kg climbs a set of stairs that reach ground level? Which quantities are the same for are 3 m high. How much gravitational potential energy the two blocks? does she gain? a. gravitational potential energy b. kinetic energy C. speed d momentum 75. A 1200-kg frictionless roller coaster starts from rest at a height of 24 m. What is its kinetic energy when it goes over a hill that is 12 m high? 76. You reach out a second-story window that is 5 m above the sidewalk and throw a 0.1-kg ball straight upward with 6 J of kinetic energy. a. What is the ball's gravitational potential energy when it is released? b. What is the ball's gravitational potential energy just before hitting the sidewalk? C. What is the ball's kinetic energy just before hitting S m the sidewalk? d. How would the answer to part (c) change if the ball had initially been thrown straight down with 6 J of kinetic energy? 77. What average power does a weight lifter need to lift 300 Ib a distance of 4 ft in 0.8 s? 78. If an 80-kg sprinter can accelerate from a standing start to a speed of 10 m/s in 3 s, what average power is 71. A 145-g baseball is thrown straight upward with kinetic generated? energy 8.7 J. When the ball has risen 6 m, find (a) the 79. If a CD player uses electricity at a rate of 15 W, how much work done by gravity, (b) the ball's kinetic energy, and energy does it use during an 8-h day? (c) the ball's speed. 80. If a hair dryer is rated at 1500 W, how much energy does 72. What is the gravitational potential energy of a ball with it require in 5 min? a weight of 50 N when it is sitting on a shelf 1.5 m above