help, please (1 Viewer)

[Sirius Black]

i was just doing revision and gotta lots of questions to ask

Ex1. a train travels at 10m/s around a bend shaped in the arc of a circle of radius 100m
a) Calculate the resualtant force acting on the train
b)Calculate the centripetal force acting on the train
in this case, are the resultant force and centripetal force the same?

thanks a lot

 

[+:: $i[Q]u3 ::+]

yes they are the same.
because the centripetal force is the one that keeps it going round in the arc. it is the only force in the x direction.
the forces in the y direction cancel out.

 

[saves.the.day]

I never knew centripital force was in the HSC syllabus?

To answer your questions, Force centripital is given by Fc = -(mv^2)/r

And So centripital force can be simply calculated by substituting in values. For resultant force, I would work out the centripital acceloration and substitute that into good old F=ma

ie. let a = Centripital acceloration
a= (v^2)/r
Substitute a into F=ma
F=(mv^2)/r

Notice that they are the same equation, however, the sign is different. This makes sense though as it satisfies Newtons third law that every force has an equal and opposite force.

However, with the values given (only knowing r and v) is not sufficient to find the Force as mass of the train is also required.

 

[xiao1985]

uhm... i have to say that i disagree... keep in mind that

centripetal force is ficticious... it is really substitution of the resultant forces on the mass...

therefore, there's no centripetal force if there is no resultant force on the train...

the resultant force would be the centripetal force on the train...

 

[elizabethy]

hey , how do u guys remember all this....i forgot physics long time back ...lolzz !!

 

[perfectionist]

they went to selective schools, hence, real smart

 

[elizabethy]

yeah cud be, but i don't even want to remember it!!!!!

 

[xiao1985]

Originally posted by perfectionist
they went to selective schools, hence, real smart

lolz... nah, i do b sci/b comm that's y.... =)

in fact i am a lot dumber than i look.... ^^

 

[lil_star]

yeah yeah xiao......u are smart thats why u reply or may be u have REAL interest in physics....i liked physics...but i dont post alot in physics...i loved ipt to i post there (always)...its just about dedication and love for a subject.....i better not start

 

[xiao1985]

nah, i am not smart!!! i told u pplz!!! i noe heaps of pplz who are reallie smart @@

i am just doing b sci/ b comm./... doing phys 1901 as my first yea degree, and happen to have learnt that in my lectures =)

 

[elizabethy]

ah okey...dats y u kinda remember it!!!

 

[lil_star]

^^lolz....hmmmmm i dont think thats the reason i still remember IPT i just love it