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Physics: Post your doubts here!

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hope4thebest

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Jiyad Ahsan said:
viscosity relates somewhat to the fluidity of a fluid (in our case, liquids).. it sort of describes a fluids resistance to flow
for example
Oil is a more viscous fluid (compared to water), it flows slowly and when you take Oil in a bottle, put an object on its surface and it will move down quite slowly.. that force that sort of resists the force of gravity pulling the object down is the viscous force.
On the other hand water flows more easily and has a smaller viscous force.
imagine swimming, you would find it easier to swim in water than in Oil, since Oil would put up a lot of resistance (viscous force) against your movement
In most cases, you may assume that a denser liquid will be more viscous and hence have a higher viscous force
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Thanks brother for the explanation!
 
TaffsAsLevel

TaffsAsLevel

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Sara syed said:
can some one explain october november 2009 questions 15,13,6
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w09_qp_11.pdf
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For 15 ElasticPE is converted to KE and it moves both sides so more stretched it adds up. So add both KE that is the EPE stored then

For 13, T=F=3/0.05=60N so torque at P is 60x0.075 Nm I took the radius because wheel Q is driven from the centre so from that point to the top of wheel Q are the distances between the forces


for 6, If you see the pattern of the graph, it is very similar to the trajectory or path of the ball so y is displacement
 
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Sara syed

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TaffsAsLevel said:
For 15 ElasticPE is converted to KE and it moves both sides so more stretched it adds up. So add both KE that is the EPE stored then

For 13, T=F=3/0.05=60N so torque at P is 60x0.075 Nm I took the radius because wheel Q is driven from the centre so from that point to the top of wheel Q are the distances between the forces


for 6, If you see the pattern of the graph, it is very similar to the trajectory or path of the ball so y is displacement
Click to expand...
thx
for 15. when i add (0.5x2x2^2) and 0.5x1x2^2 i get 6 J but the answer is 12J
 
TaffsAsLevel

TaffsAsLevel

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Sara syed said:
thx
for 15. when i add (0.5x2x2^2) and 0.5x1x2^2 i get 6 J but the answer is 12J
Click to expand...

Speed is 2 ms^-1 is only for the 2 kg trolley

See, this is a momentum problem and we know the initial momentum is zero so the right equals the left (this is similar to explosion momentum) therefore m1v1=m2v2 if you see that m and v are inversely proportional so if the m2/m1=2 (you see its 2kg and 1kg) so v2/v1=1/2 (because the momentum is equal we have to make it equal get it?) and we got the other speed for the 2 kg so the other 1 kg will have double speed of the greater mass hence we can assume it is 4 ms^-1. Now get the KE for the individual and add up as I have said you will end up 8+4=12J so D
 
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