1. What is the weight of a 2 kg mass at the surface of the earth where g=9.81 m/

Question

1. What is the weight of a 2 kg mass at the surface of the earth where g=9.81 m/sec^2? 2. How much energy, in Joules, does it take to lift this mass 2 meters? 3. If this takes 3 seconds, how much power is required? 4. What is the kinetic energy, in Joules, of a 2 kg mass moving at a speed of 5 m/sec? (Show all your work, especially units conversions!) 5. How much energy, in ft-lbf, does it take to lift a 3 pound weight 4 feet at the surface of the earth where g=32.2 ft/sec^2? 6. What would the answer to question 5 be if you were lifting a 3 pound mass?

Explanation / Answer

1. wieght= 2*9.81
           = 19.62 N
2. woek done= mgh
                   = 19.62*2
                   =39.24 J
3. power= (39.24)/3
            =13.08 W
4. kinetic energy= (1/2)mv2
                        =(1/2)*2*(5)2
                        =25m/s
5. energy = 3*4
              =12 lb-ft
6. energy= 3*32.2*4

             =386.4 lb-ft

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