Mathematics: Post your doubts here!

nehaoscar

nehaoscar

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TheJDOG said:
You mean A and C? It says the whole system is in equilibrium , so for A and C to stay in equilibrium , the tension in the strings they are attached to must be equal to their weights respectively, thus first string has a tension of 5.5 N and the other string has a tension of W N
In other words, just resolve at A and resolve at C
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Ohh yes! thankyou soo much! :)
 
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Fate0

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Ahmed Aqdam said:
Work done by engine is the same as work done by driving force. The driving force is provided by the engine.
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Thankyou very much.

I have another question. If you or anyone else can answer me , that would be great.

So for motion up a slope, for example a lorry, the examiner uses a number of formulas.

in 9707/42/M/J/12 Q6 ii) he uses WD by car’s engine = (Gain in PE + WD against resistance) + KE gain while in a similar question, in 9709/42/O/N/11 Q6, he uses
WD by DF = PE gain + WD against resistance – KE loss.

Can you please explain the difference to me? When to subtract several forces or add them? I'm also confused whether to add WD against resistance or subtract it. :/

Thankyou.
 
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ashcull14

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Fate0 said:
Thankyou very much.

I have another question. If you or anyone else can answer me , that would be great.

So for motion up a slope, for example a lorry, the examiner uses a number of formulas.

in 9707/42/M/J/12 Q6 ii) he uses WD by car’s engine = (Gain in PE + WD against resistance) + KE gain while in a similar question, in 9709/42/O/N/11 Q6, he uses
WD by DF = PE gain + WD against resistance – KE loss.

Can you please explain the difference to me? When to subtract several forces or add them? I'm also confused whether to add WD against resistance or subtract it. :/

Thankyou.
Click to expand...
when a certain quantity decreases u need to subtract it like for KE frmula= 1/2mv^2-u^2
(usually in case of upward inclined plane motion)
so if v is less than u it develops a - negative sign for eg if v=5 nd u =7 then 1/2 m (5^2-7^2) = 1/2 m (25-49) = a - value

and for WD against Fr = its only subtracted to find out some other energy change

if Friction or resistance is present:- (inclined plane)
Wd by driving forc = gain in PE + gain or loss in KE + WD by Fr
suppose change in KE is to b found out and ure given WD by Dr, change in Gpe and WD by Fr then
change in KE would be = WD by Dr - (gain in GPE+WD by Fr) ...........here is the case when u subtract wd by fr from a quantity
Hope u get it
 
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