Question

The cable of the 1700 kg elevator cab shown the figure snaps when the cab is at rest at the first floor, where the cab bottom is a distance
d = 4.6 m
above a spring of spring constant
k = 0.12 MN/m.
A safety device clamps the cab against guide rails so that a constant frictional force of 4.6 kN opposes the cab's motion. (Assume that the frictional force on the cab is negligible when the cab is stationary.)
A) Find the speed of the cab right before it hits the spring
B)Find the maximum distance x that the spring is compressed (frictional force still acts during compression)

Answer 1

C) Find the total distance the cab will bounce back up the shaft
D)Using conservation of energy, find the approximate total distance the cab will move before coming to rest.

Answer 2

@freckles

Answer 3

@IrishBoy123

Answer 4

I'm having a hard time guys I got part A it's 8.08m/s

Answer 5

I found B. x=1.07m

Answer 6

I got C. It goes up 3.23m

Answer 7

I just found the solution to this problem only with different numbers, but I don't understand what they're doing for the last part. I'll post so you can see maybe you'll be able to understand.

Answer 8

http://www.slader.com/textbook/9781118230718-fundamentals-of-physics-10th-edition/207/problems/63/

Answer 9

Want me to post how I got those answers?

Answer 10

ok I think I found some formulas...

and I'm guessing g=9.8 something is a given like some kind of kinetic energy thingy

Answer 11

we're supposed to know g so yes

Answer 12

I'm trying something right now It's gonna take forever but I think I'll be able to find the total distance

Answer 13

Going to copy and paste your problem here so I don't have to scroll up when typing this:
The cable of the 1700 kg elevator cab shown the figure snaps when the cab is at rest at the first floor, where the cab bottom is a distance
d = 4.6 m
above a spring of spring constant
k = 0.12 MN/m.
A safety device clamps the cab against guide rails so that a constant frictional force of 4.6 kN opposes the cab's motion. (Assume that the frictional force on the cab is negligible when the cab is stationary.)
\[m=1700 kg \\ d=4.6 m \\ k=0.12 \cdot 10^{6} \frac{N}{m} \\F_f=4.6 \cdot 10^{3} N \\ d_{eq}=\frac{ m \cdot g}{k}=\frac{1700 \cdot 9.8}{0.12 \cdot 10^{6}}=0.1388 \overline{3} \text{ or } \frac{833}{6000} \approx 0.1388 \\ \\ d_{eq} \text{ is the distance the spring is compressed when the cab comes to rest } \]



\[m \cdot g \cdot (d+d_{eq})=F_f \cdot D_{total } \]
should plug in the numbers and solve for distance total which is D_(total)

Answer 14

I just finished the really long way I told you about and got 16.7 which is correct when you plug in all the numbers for yours do you get the same? I'm curious

Answer 15

I got 17 but it asks for an approximation so that is right. Mine is exact lol took about 20min.

Answer 16

that means something is off about that one formula
and that this other formula I have is right
because the first one I got 17.something
and this other one I got 16.9

Answer 17

what's the formula that gave you 16.9?

Answer 18

\[m \cdot g (d_{eq}+d)=\frac{1}{2} k \cdot d_{eq}^2+F_f \cdot D_{total }\]

Answer 19

for some reason this one site as the 1/2*k*d_eq^2 thingy
while this one doesn't

Answer 20

but there is another mistake in this one site

Answer 21

http://www.myfavoritetutor.net/conservation-of-energy-1/
http://www.dhouts.com/unit_2_slns.pdf

Answer 22

I thought the explanation on that first site was better
but I think that there is mistakes on the first site

Answer 23

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CCQQFjABahUKEwibsv_MxPjIAhWDSiYKHVF4D9Q&url=http%3A%2F%2Fwww.dhouts.com%2Funit_2_slns.pdf&usg=AFQjCNEdFoFK3PmjBS0mr5F87u2habJQVA
just in case second one doesn't work

Answer 24

for example on that first site they said k=.15*10^(-6) N/m
instead of .15*10^6 N/m

Answer 25

The 2nd one works. Now how did you know Deq was mg/k??

Answer 26

That's an equation I wasn't given in class is why I ask.

Answer 27

that is what the first site explains
does spring force+frictional force-gravitational force=0
mean anything to you?

Answer 28

that Deq=mg/k is what we get if we assume the frictional force is 0

Answer 29

which is when the cab is going nowhere

Answer 30

Sounds like a modification of the formulas I know. Usually we say -frictional force

Answer 31

That makes perfect sense

Answer 32

well in all honesty I know nothing about physics
I just look up formulas and plug in numbers :p
I guess some of it makes sense though

Answer 33

LMFAO

Answer 34

Dude your pretty smart if your figuring out physics problems and haven't been taught physics.

Answer 35

You have to be really good at math I'm impressed freckles you have a degree?

Answer 36

I do have a math degree with no physics background whatsoever. If I can find a formula, I think I can help you... I might not be so good on the explanation part of it though .

Answer 37

That explains it, physics is just applied math and you seem to be able to understand the formulas really well. I can't wait till i'm at your level of intellect freckles Thanks for your help man I appreciate it.

Answer 38

How do i give you a medal?

Answer 39

lol... You don't have to but normally there is a best response button.

Answer 40

Oh that's it? just gave you one.

Answer 41

I will give you one for all your hard work and effort you had put into before I got here. And also I'm really not that smart. Getting a degree just made me feel how dumb I really am. :p
Like there is so much math and I do not know it all.

Answer 42

best response=medal

Answer 43

good to know and i agree hopefully by the time i'm 45 i'll be well rounded in every subject i want to be near expert level in the math and sciences

Answer 44

I have already accepted I will never be good in the language/english studies

Answer 45

Maybe okay... but not great.

Answer 46

lol same here

Answer 47

Don't get to 45 too fast!
Goodnight.

Answer 48

night man thanks again and i'm not gonna close this question because i want to come back to it later.

Answer 49

also I'm not a man

Answer 50

but I know what you mean man :p

Answer 51

I love meeting women that are smarter than i am

Answer 52

lol

Answer 53

have a good evening now rest well

Answer 54

I don't know if I'm smarter than you.

Answer 55

you too