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elevator problem - urgent help!
The cable of the 1800 kg elevator snaps when the elevator is at rest at the first floor, where the cab bottom is a distance d = 3.7 m above a cushioning spring whose spring constant is k = 0.15 MN/m. A safety device clamps the elevator against guide rails so that a constant frictional force of 4.4 kN opposes the motion of the elevator.
(image attached - i don't know how to make it embedded, sorry)
(a) Find the speed of the elevator just before it hits the spring._____ m/s
(b) Find the maximum distance x that the spring is compressed.______ m
(c) Find the distance that the elevator will bounce back up the shaft._____m
(d) Using conservation of energy, find the approximate total distance that the elevator will move before coming to rest._____m
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alrite let's see...
a) I've gotten the first answer by dKinetic + dPotGrav (or Ug) + E thermal (from friction) = 0 from conservation of energy... solve for V final from the kinetic part... 7.37ms-1
b) i believe it should be -1/2mv^2 - mgS + 1/2kS^2 + F(of friction)*S = 0 but I'm not sure if I'm getting the signs wrong... should my answer be negative because its compressing or not?... not getting the right answer... help please!
c) now i need my result from b) as x and is it 1/2kx^2 = mg(d up) + Friction(s +d up) solve for (d up)... Note: not sure if should just use answer from b) times the friction force or is it friction * (d up)... instead of what my equation says...?
d) to be honest I'm sorry but i have no clue to this one... and without b) and c)... I'm having trouble understanding it...
i hope some1 can help me out?! thanks in advance!
The cable of the 1800 kg elevator snaps when the elevator is at rest at the first floor, where the cab bottom is a distance d = 3.7 m above a cushioning spring whose spring constant is k = 0.15 MN/m. A safety device clamps the elevator against guide rails so that a constant frictional force of 4.4 kN opposes the motion of the elevator.
(image attached - i don't know how to make it embedded, sorry)
(a) Find the speed of the elevator just before it hits the spring._____ m/s
(b) Find the maximum distance x that the spring is compressed.______ m
(c) Find the distance that the elevator will bounce back up the shaft._____m
(d) Using conservation of energy, find the approximate total distance that the elevator will move before coming to rest._____m
--------------------
alrite let's see...
a) I've gotten the first answer by dKinetic + dPotGrav (or Ug) + E thermal (from friction) = 0 from conservation of energy... solve for V final from the kinetic part... 7.37ms-1
b) i believe it should be -1/2mv^2 - mgS + 1/2kS^2 + F(of friction)*S = 0 but I'm not sure if I'm getting the signs wrong... should my answer be negative because its compressing or not?... not getting the right answer... help please!
c) now i need my result from b) as x and is it 1/2kx^2 = mg(d up) + Friction(s +d up) solve for (d up)... Note: not sure if should just use answer from b) times the friction force or is it friction * (d up)... instead of what my equation says...?
d) to be honest I'm sorry but i have no clue to this one... and without b) and c)... I'm having trouble understanding it...
i hope some1 can help me out?! thanks in advance!