Ranking springs in terms of spring constant

AI Thread Summary
The discussion revolves around determining the spring constants of different spring arrangements using Hooke's law. It highlights that the spring constant is proportional to the mass and inversely proportional to the distance the spring stretches. The initial confusion stems from misinterpreting the diagrams and the arrangement of springs, which are either in parallel or series, affecting their overall spring constant. The correct understanding is that springs in parallel have greater spring constants than those in series, leading to the conclusion that the answer key is accurate in ranking the springs. Ultimately, the key takeaway is that the configuration of springs significantly influences their effective spring constant.
Avalanche
Messages
23
Reaction score
0

Homework Statement



untitled_zps8b86c45b.jpg


Homework Equations



Hooke's law. F = kΔx
ω = sqrt(k/m)

The Attempt at a Solution


For part A

F = mg = kΔx
k = mg/Δx

g is a constant so the spring constant is proportional to the mass and inversely proportional to the change in distance that the spring stretches

My answer is from smallest to largest spring constant: c < A = B < D

But the answer key says the answer is c < B = D < A

What am I doing wrong?
 
Physics news on Phys.org
Avalanche said:
My answer is from smallest to largest spring constant: c < A = B < D
But the answer key says the answer is c < B = D < A
That doesn't really constitute posting your attempt at a solution. You need to explain your reasoning.
 
haruspex said:
That doesn't really constitute posting your attempt at a solution. You need to explain your reasoning.

Avalanche said:

Homework Statement



F = mg = kΔx
k = mg/Δx

g is a constant so the spring constant is proportional to the mass and inversely proportional to the change in distance that the spring stretches

Greater the mass, greater the spring constant. Longer the spring stretches, smaller the spring constant. Since C stretches by the largest amount and has a mass of only m, the spring constant is the smallest. A and B stretches by the same amount and have the same mass, the spring constants are equal. C has the largest spring constant because it stretches the spring by the same amount of A and B but has a larger mass.
 
Avalanche said:
Greater the mass, greater the spring constant.
You seem to be equating the attached mass to the tension in the spring. That is not correct. The diagrams are not showing how the spring would be extended if subjected to the weight of the attached mass. For a start, the systems are horizontal, not vertical.
For this part of the question, ignore the masses. The diagrams are merely showing arrangements made by connecting up copies of some standard spring: two in parallel (A), two in series (C), or just one by itself (B, D).
 
Looking at the answer, I assume springs in parallel have greater spring constants, then springs by itself and springs in series have the smallest spring constant.

Is there a reason for this? Like an equation/relationship?
 
Avalanche said:
Looking at the answer, I assume springs in parallel have greater spring constants, then springs by itself and springs in series have the smallest spring constant.

Is there a reason for this? Like an equation/relationship?
Suppose you have two identical springs with coefficient k. If one is stretched by x it is under tension kx. If I put two in parallel, what force will I need to pull with to get an extension of k (each)?
Then try the in series case.
 
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
I was thinking using 2 purple mattress samples, and taping them together, I do want other ideas though, the main guidelines are; Must have a volume LESS than 1600 cubic centimeters, and CAN'T exceed 25 cm in ANY direction. Must be LESS than 1 kg. NO parachutes. NO glue or Tape can touch the egg. MUST be able to take egg out in less than 1 minute. Grade A large eggs will be used.
Back
Top