1:P
Q1) Four athletes are standing at the corners A,B,C and D of a square of side l.They simultaneously start running,such that A runs towards B,B runs towards C,C runs towards D and D runs towards A,each with velocity v.They will meet at O,after a time(where O is center of the square)
a) l/2v b)√2l/v
c)l/√2v c)l/v
Q2)If at a height of 40 m,the direction of a motion of a projectile makes an angle ∩/4 with the horizontal,then its initial velocity and angle of projection are respectively?
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9 Answers
62In the first question, it is a standard question which you may have missed.
See the funda here is that the distance is L
the relative velocity VA/B is always v.
The time taken will be Relative distance by relative velocity = L/v
Another mistake hidden :P
62Q2)If at a height of 40 m,the direction of a motion of a projectile makes an angle ∩/4 with the horizontal,then its initial velocity and angle of projection are respectively?
At a height of 40m,
u cos 45 = vy(t) = √u2 sin2 45 - 2gh
Using this, find u
Mistake hidden :)
1how cn we find u using that eq.????
putting value of cos 45 and sin 45 the eq we get is
-2gh=0
62let intiatl velocity be uxi+uyj
Final yy can be found in terms of uy
Now at this time, the angle is 45 degree hence ux=vy
1Nishant your answer to 1st question is right but method is not correct. The relative velocity of A with respect to B is alway √2 v . Its the velocity of approach that is v and he has to approach a total distance of l so answer is l/v.
1i don't think even this one is correct
as per soln given is book
At start the velocity of athlete at A is v along AB.The component of this velocity along AO
=v cosθ =v/√2
dist AO=1/2 AC=l/√2
so time taken =l/v
62honey what kapil has written is absolutely correct..
what is given in your book is also absolutely correct...
They are two different approaches.. and i like the approach of kapil..
This is also a stanadard approach which is there in many books.
(This is what i was trying to say .. but then this question has kind of become so standard that i overlooked the logic while typing ;)