Physics question help please forces

13

Hi, please could I have some help on this question? My answer is incorrect but I’m unsure where I’ve gone wrong (I’ve attached my working below.)
Here are the links: https://ibb.co/C8mzWkq
https://ibb.co/QDK31Gv
https://ibb.co/4MzQgLB

Thank you!

Reply 1

Joinedup

20

it looks like you've you'd tried to work done = FS

but that isn't correct for springs because the force increases as the extension increases which is unlike (for instance) a mass being decelerated by a constant braking force.
The work done compressing the spring by 0.1cm from 1.7cm to 1.8cm is greater than the work done compressing the spring by 0.1 cm from 0.6cm to 0.7cm because the the force is greater between 1.7and 1.8cm than it is between 0.6 and 0.7cm

The formula for elastic potential energy stored in a spring is 1/2 kx^2 and extension x is defined as the displacement from the position where force is zero (which isn't shown on the graph provided)
we can however quite easily show that the graph would pass through (0,0) if the axes were continued so we're happy about that.

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Reply 2

Nitrotoluene

11

Original post

by anonymous56754

Hi, please could I have some help on this question? My answer is incorrect but I’m unsure where I’ve gone wrong (I’ve attached my working below.)
Here are the links: https://ibb.co/C8mzWkq
https://ibb.co/QDK31Gv
https://ibb.co/4MzQgLB
Thank you!

You have to identify the variables involved:

1.

The force exerted on the spring

2.

The compression of the spring

You have to determine the spring constant k.
You have to calculate the elastic potential energy (Ep=1/2kx^2).

Bye,
Sandro

(edited 1 year ago)

Reply 3

Eimmanuel

Study Forum Helper

15

Original post

by anonymous56754

Hi, please could I have some help on this question? My answer is incorrect but I’m unsure where I’ve gone wrong (I’ve attached my working below.)
Here are the links: https://ibb.co/C8mzWkq
https://ibb.co/QDK31Gv
https://ibb.co/4MzQgLB
Thank you!

Why is your compression Δx = 0.012?
Did you misread the graph?

Reply 4

anonymous56754

OP

13

Original post

by Eimmanuel

Why is your compression Δx = 0.012?
Did you misread the graph?

I did 1.8-0.6 by choosing the first and last point on the line

Reply 5

Joinedup

20

the figure is a graph fragment.
you are interested in the energy stored between x=0 and x=1.8cm

Reply 6

Eimmanuel

Study Forum Helper

15

Original post

by anonymous56754

I did 1.8-0.6 by choosing the first and last point on the line

Joinedup mentioned that the graph is a “cut-off” graph that does not show the whole story, and the question is interested from x = 0 to x = 1.8 cm.

Your working is good except for the Δx.

Physics question help please forces

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