What am I doing wrong in my calculations

In summary, the problem involves three masses (m1 = 3.3 kg, m2 = 9.9 kg, and m3 = 6.6 kg) hanging from three identical springs in a motionless elevator with a spring constant of 229.57 N/m. The elevator then moves downward with a velocity of v = -2.3 m/s but accelerates upward with an acceleration of a = 4.8 m/s2, resulting in the top spring being extended from its unstretched length by 20.987 cm. The tension in the top spring is not explicitly stated, but can be determined by starting with the free body diagram of the bottom mass and working up.
  • #1
aruji73
19
0
What is the distance the upper spring is extended from its unstretched length?
Now, three masses m1 = 3.3 kg, m2 = 9.9 kg and m3 = 6.6 kg hang from three identical springs in a motionless elevator. The springs all have the same spring constant of 229.57N/m

Now the elevator is moving downward with a velocity of v = -2.3 m/s but accelerating upward with an acceleration of a = 4.8 m/s2. (Note: an upward acceleration when the elevator is moving down means the elevator is slowing down.)

What is the distance the upper spring is extended from its unstretched length?
cm


I did

(3.3(9.8+4.8))/229.57=0.20987 m =20.987 cm
 
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  • #2
aruji73 said:
What is the distance the upper spring is extended from its unstretched length?
Now, three masses m1 = 3.3 kg, m2 = 9.9 kg and m3 = 6.6 kg hang from three identical springs in a motionless elevator. The springs all have the same spring constant of 229.57N/m

Now the elevator is moving downward with a velocity of v = -2.3 m/s but accelerating upward with an acceleration of a = 4.8 m/s2. (Note: an upward acceleration when the elevator is moving down means the elevator is slowing down.)

What is the distance the upper spring is extended from its unstretched length?
cm

I did

(3.3(9.8+4.8))/229.57=0.20987 m =20.987 cm
That looks good to me.

Is there a problem regarding significant digits?
 
  • #3
Hi I am not sure my answer is supposed to be in cm but I am sure I have done it right puzzling indeed
 
  • #4
In your problem you have mensioned three springs and three masses. Whether the springs are connected with each other? If yes, who?
 
  • #5
springs are connected is m1 at top is connected to m2 in middle which is connected to m3 in the bottom
 
  • #6
So, the spring at the top is supporting, directly or indirectly, all three masses? Won't that increase the tension in it?
 
  • #7
this is the pic
 

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  • #8
Right, so what is the tension in the top spring? If you're not sure, start with the free body diagram of the bottom mass and work up.
 

FAQ: What am I doing wrong in my calculations

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