Impulse momentum theorum with a spring

AI Thread Summary
The discussion revolves around calculating the contact time between a glider and a spring during a collision. The initial attempt at using the impulse-momentum theorem resulted in confusion regarding the correct values for force and mass, particularly the need to convert grams to kilograms. Participants highlighted the importance of using average force rather than peak force for accurate calculations. One contributor clarified their solution by finding the area of a triangle to represent impulse, leading to a formula involving the maximum force and change in time. The conversation also touched on the implications of momentum change, questioning whether it should be considered zero or double due to direction reversal.
powerofsamson
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Homework Statement


A 700 g air-track glider collides with a spring at one end of the track. The figure shows the glider's velocity and the force exerted on the glider by the spring.

How long is the glider in contact with the spring?

knight_Figure_09_11a.jpg

knight_Figure_09_11b.jpg

Homework Equations



F(t_1-t_2)=mv_2-mv_1

The Attempt at a Solution


I have the force as 36N, v_1 as -3, v_2 as 3.
When I plug this into the equation I get
change in t = (700*3-700*(-3))/36=116.6

I know this has to be wrong but I'm confused which variable I have wrong. Maybe the force?
 
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You need to convert 700 g to kg. Other than that, I think your solution is correct.
 
change in t = ((.7*3)-(.7*-3))/36 = .116 s is also wrong.
 
Sorry, you need to use the average force. The 36 N is the peak force.
 
I'm still stuck on this one. I know that i can calculate avg force by impulse / change in time, but I'm not sure how to find avg force in this situation.
 
In case anyone else has a similar problem I'll explain how I found the answer. I found the area of the triangle with. A = .5 * (36, force max) * change in t. A is equal to weight in kg * v_1 - (weight in kg * v_2). Therefore 4.2 = .5 (36) * change in t.
 
powerofsamson said:
In case anyone else has a similar problem I'll explain how I found the answer. I found the area of the triangle with. A = .5 * (36, force max) * change in t. A is equal to weight in kg * v_1 - (weight in kg * v_2). Therefore 4.2 = .5 (36) * change in t.

I know this is an old message but this poster states he solved the problem by finding.

(simply restating correct solution posted in quotes here)

A=area

A=.5(Fmax)Δt

A=mv1-mv2

I think? I don't understand what equations the poster was trying to write out.

Wouldn't the change in momentum be zero since the final and initial speeds are equal?

Or would it be double the current momentum because of the change in direction?
 
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