1)A 1.66 m tall person lifts a 2.34 kg book from the ground so it is 2.44 m abov
ID: 2116250 • Letter: 1
Question
1)A 1.66 m tall person lifts a 2.34 kg book from the ground so it is 2.44 m above the ground. What is the potential energy of the book relative to the ground? What is the potential energy of the book relative to the top of the person's head? Calculate the work done by the person related to the answers in parts (a) and (b). 2) A 74.4-kg bungee jumper jumps from a bridge. She is tied to a bungee cord whose unstretched length is 12.2 m, and falls a total of 32.8 m. Calculate the spring stiffness constant k of the bungee cord, assuming Hooke's law applies. Calculate the maximum acceleration experienced by the jumper. 3) A 19.4 kg child descends a slide 3.20 m high and reaches the bottom with a speed of 2.34 m/s. How much thermal energy due to friction was generated in this process? 4) A skier traveling 12.4 m/s reaches the foot of a steady upward 16.6Explanation / Answer
1)
ANS :
m*g*h = PE = 2.34*9.8*2.44 = 55.954 J
PE = 2.34*9.8*(2.44-1.66) = 17.89 J
Work done will be same = 55.954 J
2)
74.4 *9.8 = k*(32.8 -12.2)
k = 35.39 N/m
Max acceleration = 9.8 m/s^2
3)
Energy lost = 19.4*9.8*3.2 - 0.5*19.4*2.34^2 = 555.27 J
4)
0.5*m*12.4^2 = m*9.8*10.8 *sin 10.8 + mew*m*9.8*10.8 ;
mew = 0.4407
5)
Time = Energy / Power = 314*9.8*13/1690 = 23.67 s
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