1LOL!....well biologically in a special case its a & b too :P
[one who guesses it right wat is the special case gets a apple ipod from me :)]
When one swims across a flowing river,maximum energy is spent in
a)first 1/3rd of distance
b)second 1/3rd of distance
c)last 1/3rd of distance
d)equal energy is spent throughout
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9 Answers
1
1THe answer given is a).
In first 1/3rd if he haas to begin his motion,
then why more energy is spent??Explain.
Can u give some mathematical explanation
39To change your state of inertia(motion/rest to rest/motion), some energy would obviously be required isn't it?
The first 1/3rd of the journey is just an approximation I guess..
After that the journey across the river is partly aided by the river's own flow.
1yaar its pretty simple....whichever book u refer to...look for a term called inertia
it takes extra effort to change the state of a body!!!
when the swimmer starts swimming....he has to change his state from rest to come into motion
acc to me its a conceptual question n therefore there wont be a mathematical expression...nt sure!!!
49i d k...i have different approach to this...
clauses to my approach::
a) infinite acceleration not allowed
b) constant resistive force applied by water throughout the journey
so, if the man tries to move with constant velocity, at first he has to accelerate from rest..(V=at)
so initial part of the journey will make the man exert a force of F=ma+f where f is the resistive force by water and m is mass of the man.
after the required speed is attained, the man just applies the force F=f
thus work done in initial part of journey(i mention initial part not first one-third or anything) will be more than the rest part....thus more energy spent in initial part.
next if the man tries to move with constant acceleration throughout the journey then the constant force applied by him is F=ma+f(usual meanings)
so the work done by him is constant throughout..
if the man tries to move with increasing acceleration then he applies more force towards the end of the journey .. so max energy spent in the latter part of journey..
if the man tries to move with a decreasing acceleration then more force applied at initial stage of journey and thus, more energy spent in initial part..
thus, the question does not mention clearly whichever of the cases it is demanding..
COMMENTS ON THIS SOLUTION ARE WELCOME!!
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1@organic...
if u r a guy...m damn sure we r bros....n if u r a gal....m damn sure v r bro n sis
sometimes even i look at the question by this angle n get confused
bt since nothing is given in the question....i think we shud just simply apply the basic concepts of some weird thing known as physics!!!:P
the thing u r saying is abt acc n vel
bt it can be argued that if the man just jumps in the river n leaves himself free....n just moves his hand a little bit with hardly any effort...at some point he will definately reach the other end...hai na??
so thats y i applied the very basic concept of physics n dint think much...