IIT JEE , AIEEE Forum - Physics , Mechanics

ashok_p_ap

22.03.2008

Physics

1. A cubical block of mass m &edge ?a? slides down a rough inclined plane of inclination 0 with a uniform velocity. Find the torque of normal force acting on the block about its centre.

Ans. mga sin0

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2

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3. All surfaces frictionless.

(1)Speed of smaller block when it breaks off at a height h.

(2)Max. height from ground the smaller block will ascend.

(3)Show that the smaller block will land again on the larger mass.

(4)Distance traversed by the bigger block during the time the smaller block was in flight under gravity.

Ans. (1) (M²+Mm+m²) v²

{ -------------------- ? 2gh}^1/2

(M+m)²

(2) Mv²(4) 2mv [Mv²-2(M+m)gh]^1/2

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2g(M+m) g(M+m)^3/2

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4. A small block of superdense material has a mass M_e/2. It is situated at a height ?h? above the earth?s surface.(h<<R_e).

Find its speed when the height reduces to ?h?/2.

(M_e=6x 10²⁴ kg). Ans.(2gh/3)^1/2

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5. What is radial equilibrium?

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6. In both cases, 0=tan^-1 (a/g).

How to know whether cart is moving on an incline(with uniform velocity) or on a horizontal plane (accelerated)?

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LAMPARD

4>there are two fundamental eqn --
conservation of energy
loss of pe=GmM[1/(R+h/2) - 1/(R+h)]
=gain in ke=1/2MV^2+1/2mv^2
where M,V FOR EARTH
ans m,v for block

another eqn--
conservation of momentum--
MV=mv

from the above above we can eliminate V
and after putting GM/R^2=g

we get the ans-v^2=2gh/3

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