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Physics: Post your doubts here!
- Thread starter XPFMember
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ans is BKE= PE+KE
1/2(m)(28)^2=m(g)(22)+1/2(m)(v)^2
The initial KE is converted into PE when it leaves the exit road since the road is 22m higher than the motorway. Since they ask the final speed this means that not all KE is converted into PE, hence there is remaining KE
They say that wheel friction is constant throughout the motion. Therefore, from the graph when there is 0 velocity, the wheel friction is 8kN.
The total resistive force (wheel friction+ air resistance) at v=200 is 40kN.
Ratio= 32k/4k= 8
Is it C?
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Yess! Please could you explain?
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Why and how is it A?
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- Messages
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- Messages
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Can someone please give me notes on this states of solid liquid gas and evaporation boiling condensation melting freezing etc... because i get confused with these questions and i can't find it in the text book :/
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Why not A ?
It's evaporation because evaporation is a process which depends on the velocity of the water molecules. If the molecules at the surface possess enough energy then they are able to escape the forces that hold the molecules together and then escape as vapour. But the question states that all the molecules have the same speed, hence evaporation cannot occur
Voltmeter normally has very high resistance to make sure that current doesn't flow through it when it measures the pd across an object. It cannot be A because since the voltmeter is connected in series , the current would have to pass through the voltmeter before it can reach the ammeter. Very high resistance so no current passes through.
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So then boiling, condensation and melting don't depend on the speed of molecules? ... Then what do they depend on?
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use s=ut + 1/2 at^2 for both motions (X-Y and Y-Z)
this will give you these:
X-Y
40 = 12u + 72a
Y-Z
40 = 6v + 18a (note that the u for this motion is the v from the motion in X-Y)
So use s = 1/2 (u+v) t
and rearrange to make v the subject and substitute the values for X-Y motion so you get v = 6.67 - u
Substitute v into the Y-Z equation
Y-Z
40 = 6(6.67 - u)+ 18a
40 = 40 - 6u + 18a
0 = -6u + 18a
Form simultaneous equations:
40 = 12u + 72a
0 = -12u + 36a (multiply the Y-Z eqn by 2 to cancel the u's)
this will give a = 0.37 = A
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It's C right? I just did this question
B is wrong cause the initial force at which it is thrown is same for both, so the initial path has to be the same
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YeahIt's C right? I just did this question
but why not A
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1. Boiling: occurs at a fixed temperature, that is the boiling point of the liquid. Its a process that occurs throughout the liquid. Basically for boiling, you are heating up the entire liquid. The heat is being distributed evenly throughout the liquid and the speed of the molecules increases together. (Same for melting, since melting and boiling both absorb heat). Hence, at any temperature the speed of the molecules are the same.
2. But for evaporation, the process only occurs on the surface of the liquid. The molecules at the surface are absorbing heat from the surroundings and some of them will have enough energy to break their intermolecular forces and escape.
3. Condensation is mainly when hot vapour touches a cool surface and forms water droplets.