What am I doing wrong in my calculations

[aruji73]

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

 

[SammyS]

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?

 

[aruji73]

Hi I am not sure my answer is supposed to be in cm but I am sure I have done it right puzzling indeed

 

[rl.bhat]

In your problem you have mensioned three springs and three masses. Whether the springs are connected with each other? If yes, who?

 

[aruji73]

springs are connected is m1 at top is connected to m2 in middle which is connected to m3 in the bottom

 

[haruspex]

So, the spring at the top is supporting, directly or indirectly, all three masses? Won't that increase the tension in it?

 

[aruji73]

this is the pic

 

[haruspex]

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.