Some physics qns!
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Ok i got quite some qns. This is the result of my revision for today. XD
1) As the speed of car(whose brakes are spoilt) decreases, would the friction between wheels and land decrease too?
Wheels are hard to picture. If i decrease my horizontal force applied on a moving rubber on a table, does the friction acting against my decreasing movement decrease?
2)Air passing through a chamber with cold tubes are cooled by conduction or convection?
3) For a non-conductor, are the negative charges able to move ard? Eg if a positively charged metal bar is placed near to a non-conductor, would the negative charges be attracted to that side?
4)(hard one here XD)
A car of mass 700kg with initial kinetic energy of 560KJ and initial speed of 40m/s approaches a slope of height 3m. Note that the car does not brake.
a) Find the change in gravitational potential energy.(this is not impt i am just posting a ''fuller'' qn.)
b) Find the average frictional force on the car if the car comes to rest after 40m.
Thanks!
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1) think the other way. as the car speed up, would the friction increase? yes.
2) conduction. convection has a different definition.
3) no. that's what you should answer at least.
4) smiley face
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4 b) work done = force x distance.
work done = frictional force x distance. -
ok i understand thats what i did initially.
this is what i did. (560000- 21000(GPE)) = F (40)
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but this is assuming frictional force stays constant.
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Originally posted by SBS1984E:
but this is assuming frictional force stays constant.
nope.
this is just finding average frictional force.
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Originally posted by SBS1984E:
but this is assuming frictional force stays constant.
they asked for average frictional force. DOes this info have sth to do with like "you shldnt use energy method to solve"?
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btw the answer for my inital method is wrong. XD
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sigh... is the slope upwards or downwards?
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Originally posted by davidche:
they asked for average frictional force. DOes this info have sth to do with like "you shldnt use energy method to solve"?
Oh yea... paiseh.
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yo err sky, can solve?
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oh do you want the model solutions? again there is a reason why i asked this qn even tho i have the solutions.
The first step of the solution is t=2s(just like tat) How does he know t=2s!!
Also, i tot could use energy method to solve XD
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Urgent Help!!
Calculate the density of the ice at 0 degree...Er..Someone help pls..!! I get 1 g/cm^3 but the answer in the book say 0.909g/cm^3.
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what! ok i like this.
upwards. It is supposed to slow the car down XD
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sorry, was talking on the phone with girlfriend.
just give me the final answer.
t=2s? where did that come from?
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Originally posted by jlzk:
Urgent Help!!
Calculate the density of the ice at 0 degree...Er..Someone help pls..!! I get 1 g/cm^3 but the answer in the book say 0.909g/cm^3.
Since u posted the ans. i do it in reverse.
Take volume of 0 deg. at 11cm^3
Use D=M/V= 10/11= 0.909...91
Hence density is 0.909cm^3
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0.909g/cm^3
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the other q, the force thingie
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from the graph, ice has a volume of 11 cm cube at 0 degree celcius.
density = 10g divide by 11cm cube
= 0.909the key is the diagram
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Originally posted by MyNameisNas:
Since u posted the ans. i do it in reverse.
Take volume of 0 deg. at 11cm^3
Use D=M/V= 10/11= 0.909...91
Hence density is 0.909cm^3
But why u take 11 but not 10?Pretend you did not see the answer how u know is take 11 and not 10 cause in 0 degree they are at 11-10
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Originally posted by jlzk:
But why u take 11 but not 10?Pretend you did not see the answer how u know is take 11 and not 10 cause in 0 degree they are at 11-10
fact, water expands when it freezes into ice.
hence, it is 11, not 10. 10 is just water at 0 degree
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k i try to digest abit thanks!
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ok, now back to the other q... what is the final answer according to the answer sheet? i have no idea where the t = 2s came from.
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A car of mass 700kg with initial kinetic energy of 560KJ and initial speed of 40m/s approaches a slope of height 3m. Note that the car does not brake.
a) Find the change in gravitational potential energy-(Pe).(this is not impt i am just posting a ''fuller'' qn.)
Is that how the actual question is? the confusing part is the question did not put the point of Pe. Basically at 3m Pe=0j and at 0m Pe is 560KJ.
From wiki-cos i lazy to type- the law of conservation of energy states that energy can neither be created nor destroyed, it can only be changed from one form to another or transferred from one body to another, but the total amount of energy remains constant (the same).
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Originally posted by MyNameisNas:
A car of mass 700kg with initial kinetic energy of 560KJ and initial speed of 40m/s approaches a slope of height 3m. Note that the car does not brake.
a) Find the change in gravitational potential energy-(Pe).(this is not impt i am just posting a ''fuller'' qn.)
Is that how the actual question is? the confusing part is the question did not put the point of Pe. Basically at 3m Pe=0j and at 0m Pe is 560KJ.
From wiki-cos i lazy to type- the law of conservation of energy states that energy can neither be created nor destroyed, it can only be changed from one form to another or transferred from one body to another, but the total amount of energy remains constant (the same).
i have no idea what you trying to say though. you can find PE by using mgh?