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September 10, 2025, 02:07:22 pm
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Author Topic: Specific questions/explanations  (Read 5897 times)  Share 

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appianway

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Re: Specific questions/explanations
« Reply #30 on: June 08, 2010, 04:55:55 pm »
If it's lowered to rest (so that no further oscillation can take place), it'd mean that Fnet = 0 when it stops as otherwise the mass would experience a force and would oscillate. The lowering gently would just provide enough force so that oscillations don't occur, however, energy would be transferred to whatever is doing the lowering.

I'm not sure how complicated they want the next part to be :/ Do they want to consider the change of the centre of mass of the spring or do we presume it to be massless? I'd say it'd be the initial spring energy (=0) + gravitational energy (say that h=0.4) - the energy in the spring.
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Blakhitman

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Re: Specific questions/explanations
« Reply #31 on: June 08, 2010, 04:57:19 pm »
Yeah it didn't oscillate, the hand moves with the spring.

Ok that clears it thanks...not happy though...
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Davoo!

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Re: Specific questions/explanations
« Reply #32 on: June 08, 2010, 04:57:42 pm »
I used 9.8 for g throughout, so I got 49 for spring constant and 3.9J for the spring questions. Any marks lost here?

As far as I know, I only bunged up the mass question with 0.4kg and 0.1kg blocks. I had no idea... But I'm sure I had more docked somewhere along the way. How much was the block question worth in total?
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appianway

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Re: Specific questions/explanations
« Reply #33 on: June 08, 2010, 04:59:16 pm »
Don't worry about the two mass question. I can only think of about 2 people in Victoria who I'm sure would've gotten full marks for it because they've seen similar ones before - there might be a few more who do uni level stuff for fun, but you never know...
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TrueTears

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Re: Specific questions/explanations
« Reply #34 on: June 08, 2010, 05:02:01 pm »
na u shudnt lose marks for using 9.8 examiners are human, they will allow 9.8.
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bomb

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Re: Specific questions/explanations
« Reply #35 on: June 08, 2010, 05:04:07 pm »
appianway, im not sure if you know but the question included a frictionless pulley, will that change anything?
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appianway

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Re: Specific questions/explanations
« Reply #36 on: June 08, 2010, 05:06:07 pm »
No. The pulley won't rotate because it's completely frictionless, so even its moment of inertia won't change anything. The pulley just changes the direction of the force.
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bomb

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Re: Specific questions/explanations
« Reply #37 on: June 08, 2010, 05:08:50 pm »
Ok, the mass on the table was 0.4kg and the other was 0.1, so how would you calculate

a) the acceleration of the table mass

and

b) its kinetic energy after 1m?

Thanks.
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Blakhitman

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Re: Specific questions/explanations
« Reply #38 on: June 08, 2010, 05:11:00 pm »
The kinetic energy you need to use constant acc formula to find v then use 1/2mv^2, Consequentials there for sure...I hope.
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Twenty10

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Re: Specific questions/explanations
« Reply #39 on: June 08, 2010, 05:12:15 pm »
.8J ???
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Blakhitman

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Re: Specific questions/explanations
« Reply #40 on: June 08, 2010, 05:15:07 pm »
if you used the right acceleration (from question before)...which I didn't....
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rubiks

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Re: Specific questions/explanations
« Reply #41 on: June 08, 2010, 05:16:27 pm »
how do you find the velocity? I'm sure I did this question, I just can't remember how I did it lol
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Greggler

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Re: Specific questions/explanations
« Reply #42 on: June 08, 2010, 05:19:34 pm »
yeah there would deffs be consequentials.
considering you use accel to find v, then use v to find energy. i got 1J
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m@tty

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Re: Specific questions/explanations
« Reply #43 on: June 08, 2010, 05:26:30 pm »
Same. But I just used work lol. Force 1N left. Displacement 1 m left. All work becomes kinetic(no friction) Therefore Ek=1x1=1J lol. 

But I got the wrong force :|
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Blakhitman

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Re: Specific questions/explanations
« Reply #44 on: June 08, 2010, 05:29:15 pm »
Why is that wrong force?
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