Laws of Motion

  • Question 505
    CBSEENPH11020429

    The upper half of an inclined plane with inclination φ is perfectly smooth while the lower half is rough. A body starting from rest at the top will again come to rest at the bottom if the coefficient of friction for the lower half is given by

    • 2sinφ

    • 2cosφ

    • 2tanφ
    • tanφ

    Solution

    C.

    2tanφ
    Question 506
    CBSEENPH11020430

    A bullet fired into a fixed target loses half of its velocity after penetrating 3 cm. How much further it will penetrate before coming to rest assuming that it faces constant resistance to motion?

    • 3.0 cm

    • 2.0 cm

    • 1.5 cm

    • 1.0 cm

    Solution

    D.

    1.0 cm

    straight F.3 space equals 1 half mv squared minus 1 half straight m straight v squared over 4
straight F left parenthesis 3 plus straight x right parenthesis space equals 1 half mv squared
space straight x space equals space 1 space cm
    Question 507
    CBSEENPH11020431

    Out of the following pair, which one does NOT have identical dimensions is

    • angular momentum and Planck’s constant

    • impulse and momentum

    • moment of inertia and moment of a force

    • work and torque

    Solution

    C.

    moment of inertia and moment of a force

    Question 508
    CBSEENPH11020437

    A body A of mass M while falling vertically downwards under gravity breaks into two parts; a body B of mass 1/3 M and a body C of mass 2/3 M. The centre of mass of bodies B and C taken together shifts compared to that of body A towards

    • depends on height of breaking

    • does not shift

    • body C

    • body B

    Solution

    B.

    does not shift

    No horizontal external force is acting
    ∴ = acm =0
    since vcm= 0
    ∴∆xcm = 0

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