Finding acceleration in spring situations

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Homework Help Overview

The discussion revolves around calculating the acceleration of a duck being pulled by a spring, with given parameters such as mass, spring constant, and coefficient of kinetic friction. The problem involves understanding the forces at play, including the spring force and frictional force, as well as their impact on the duck's acceleration.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the calculation of the spring force and question the relationship between different forces acting on the duck. There is a focus on clarifying the direction and magnitude of these forces, particularly the frictional force, and how they contribute to the net force and acceleration.

Discussion Status

The discussion is active, with participants seeking clarification on the calculations and the relationships between forces. Some guidance has been provided regarding the need to differentiate between forces and to consider their directions. There is an ongoing exploration of the implications of a typing error regarding the spring stretch value.

Contextual Notes

Participants are working within the constraints of the problem statement and are addressing potential errors in the provided values. The discussion reflects a collaborative effort to ensure accurate interpretations of the forces involved.

bunk66
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Homework Statement


A duck of mass 40kg is being pulled by a spring with k = 900N/m. If μk = 0.6 between the duck and the road, find the acceleration of the duck given that the spring stretches 0.4m.

Homework Equations


Fspring = kx, where k = spring constant and x = stretch of spring
Fnet = ma

The Attempt at a Solution


Fspring = kx
F = 900N/m(0.6m)
F = 540N

That's about as far as I got before not knowing what to do next.
 
Last edited:
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bunk66 said:
F = 900N/m(0.4m)
F = 540N
Those are two different forces, so give them different names.
In which directions do they act?
How do they relate to the acceleration of the duck?
 
haruspex said:
Those are two different forces, so give them different names.
In which directions do they act?
How do they relate to the acceleration of the duck?
What exactly do you mean that they are two different forces? In the section that you quoted, isn't there only one force being calculated: the spring force?

And p.s, I made a typing error. Where it says 0.4, it should be 0.6
 
bunk66 said:
I made a typing error. Where it says 0.4, it should be 0.6
OK, that's what made me think you were referring to two different forces.
So, what is the frictional force acting on the duck (direction and magnitude)?
 
haruspex said:
OK, that's what made me think you were referring to two different forces.
So, what is the frictional force acting on the duck (direction and magnitude)?
I mixed some of the numbers apparently.

Fspring = kx
F = 900N/m(0.4m)
F = 360N

40kg x 9.8 = 392N

Ff = μk(FN)
Ff = 0.6(392N)
Ff = 236N

Fnet = Fa - Ff
Fnet = 360N - 236N
Fnet = 124N

Fnet = ma
Fnet/m = a
124N / 40kg = a
3.1 m/s2 = a

Evidently that was a lot easier than I made it out to be :redface:
 

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