# Isaac Physics question

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#1
https://isaacphysics.org/questions/metal_block

I am not sure how to do part b of this question, I have done part a b d but I am very stuck on part d
where it is accelerating, I know that V=a_n*t and s1 = 0.5*a*t^2

after the string snaps 1/2mv^2 = F_r * s2

so i thought that(mv^2)/2F_r (0.5 * a* t^2) would be the total displacement but this is wrong, I am not sure how to work this out any other way.
Last edited by Emily~3695; 2 months ago
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2 months ago
#2
(Original post by Emily~3695)
https://isaacphysics.org/questions/metal_block

I am not sure how to do part b of this question, I have done part a and c but I am very stuck on part b.

for the part where it is accelerating, I know that V=a_n*t and s1 = 0.5*a*t^2

after the string snaps 1/2mv^2 = F_r * s2

so i thought that(mv^2)/2F_r + (0.5 * a* t^2) would be the total displacement but this is wrong, I am not sure how to work this out any other way.
Part b) is about tension & acceleration ratios, not string breaking and displacements?
Last edited by mqb2766; 2 months ago
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#3
(Original post by mqb2766)
Part b) is about tension & acceleration ratios, not string breaking and displacements?
Oh Yh sorry I meant part c I forgot about part A ( I’ve done a,b and d then )
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2 months ago
#4
(Original post by Emily~3695)
Oh Yh sorry I meant part c I forgot about part A ( I’ve done a,b and d then )
The net force acting on the body is a positive constant (difference between tension and resistance) before the string breaks. Then a negative constant (-resistance) after it breaks. Just model that in terms of two distance suvats and the velocity suvat until the string breaks. Post what you try.
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#5
(Original post by mqb2766)
The net force acting on the body is a positive constant (difference between tension and resistance) before the string breaks. Then a negative constant (-resistance) after it breaks. Just model that in terms of two distance suvats and the velocity suvat until the string breaks. Post what you try.
Thank you, this is what I’ve done but I’ve definitely gone wrong somewhere but I’m not really sure how else I’m supposed to solve it:
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2 months ago
#6
Not really sure about some of the bits in your work but it looks verbose. For the first part:
s = a_n * t^2 / 2
v = a_n * t
So for the second part
s = (a_n * t)^2 / (2F_r/m)
add the 2 displacements. That should be about it (may have got the odd bit of notation wrong).
Last edited by mqb2766; 2 months ago
0
#7
(Original post by mqb2766)
Not really sure about some of the bits in your work but it looks verbose. For the first part:
s = a_n * t^2 / 2
v = a_n * t
So for the second part
s = (a_n * t)^2 / (2F_r/m)
add the 2 displacements. That should be about it (may have got the odd bit of notation wrong).
Thank you, this is what I originally thought as well but for some reason it’s not right, I’ve tried lots of different things but none of them are working.
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2 months ago
#8
(Original post by Emily~3695)
Thank you, this is what I originally thought as well but for some reason it’s not right, I’ve tried lots of different things but none of them are working.
I get it correct. Upload a pic of what you actually entered?
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#9
(Original post by mqb2766)
I get it correct. Upload a pic of what you actually entered?
I’ve got it right now, the reason I’ve been getting if wrong is because I keep writing s = ... but the answer does not need this. Thanks for your help
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