1question 1 is just visualisation...just use the fact that in elastic collision identical balls exchange velocity..
1. 3 identical balls moving together along a horizontal line with velocity v collide with 2 similar balls at rest along the same line. The collision is elastic. After the collision
a. 2 balls move with vel. v
b. 2 balls move with vel. 3v/2
c. 3 balls move with vel. v
d. 3 balls move with velocity 2v/3
2. Consider a particle of a rigid body. Its motion can be described by vectors r, \omega, ar, at and ∂ (symbols have their usual meanings). Then which of the following equations is incorrect
a. \omega = d\theta/dt
b. v = r x \omega
c. ar = \omega x (\omega x r)
d. at = ∂ x r [all the symbols are with vector signs]
3. 2 soap bubbles of radii 2r and 3r are in contact with each other. The radius of curvature of the interface between the bubbles is
a. 2r
b. 6r
c. 3r
d. r
4. A block is placed on a surface with vertical cross-section given by the equation y = x2/20 . The coefficient of friction is 0.5, the maximum height above the ground at which a block can be placed without slipping is
a. 1 m
b. 1.25 m
c. 1.5 m
d. 1.9 m [the last qstn is not a doubt,just to clarify....only the answer will do]
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11 Answers
301. (c)
2. (d) (Its a guess. I can't think of what δ is)
3. Standard formula I guess. 1r=1r1-1r2. Should be (b)
1A4) 1.25
mgsinθ = u mg cos θ
=> tan θ = 1/2 => the point is (5,5/4) .:. max height is 5/4 = 1.25
1@ashish: can u pls post the soln of qstn 1 and 2?....and ∂ is ang accn....for 3rd qstn,is the formula derivation given in hcv?
@rishabh:yes,it is 1.25 m....i dnt hv the answrs but i`m also getting the same thing....
more qstns to follow....
11i`m not sure if that is the case here....the 3 balls are moving together....
21just imagine there is a distance ∂ between the 3 balls where ∂→0
262@a, shish- for the soap bubble one do u think it can be possible ? try drawing a diag. u will understand what i mean.
1@aditya: but it is one correct multiple choice qstn....i hv the qstn paper with me..