#### mahtab_lovelygirl

i have lots of question about physic....
i hope u guys can help me. i really appreciate :)

1)
a) now that i am 50 and semi-mature. you'll never catch me bungee jumping. but let's say someone my mass(80kg) and height (1.83m) did and they used a 20m bungee cord with a k value of 500 n/m. what is the minimum height that the lunatic would need in order that he/she wont get killed?

b) if the same person was gently lowered down and the bungee cord came to equilibruim, far far would the cord stretch?

c)what is the person's speed when they have stretched the cord 8m? consider energy transfor motion.

d) what is the acceleration when the cord has been stretched?

2) an electron moving threough an electric field of 475 v/m and a magnetic field of oil experiences no force. if the electron's direction and the directions of the electric and magnetic fields are all mutually perpendicular, what is the speed of the electron? start with a sketch :P

i really need them as soon as possible for my final exam:(

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#### pete worthington

Welcome to Physics Forum..........We can help you, but you must do the work...
1a) Conservation of energy. Initial potential-gravitational energy will transform into final potential-spring energy. You have all the variables except height. As far as the persons height, that depends on how/where the person jumps from. The length of the cord must also be taken into account. Draw a picture and label positions.
1b) Hookes Law. That equation should be easy to find.
1c) Go back to your drawing. At this position you have potential-gravitational, kinetic and potential-spring. The unknown is velocity.
1d) Hookes Law and Newton's Second Law combined.

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