Laws of Motion

  • Question 497
    CBSEENPH11020401

    A particle is projected at 60° to the horizontal with a kinetic energy K. The kinetic energy at the highest point is 

    • K

    • 0

    • K/2

    • K/4

    Solution

    D.

    K/4

    Question 498
    CBSEENPH11020406

    A bomb of mass 16 kg at rest explodes into two pieces of masses of 4 kg and 12 kg. The velocity of the 12 kg mass is 4 ms−1 . The kinetic energy of the other mass is

    • 144 J

    • 96 J

    • 288 J

    • 192 J

    Solution

    C.

    288 J

    m1v1 = m2v2
    KE space equals space 1 half straight m subscript 2 straight v subscript 2 superscript 2 space
space equals space 1 half space straight x space 4 space straight x space 144 space equals space 288 space straight J

    Question 499
    CBSEENPH11020408

    A mass of M kg is suspended by a weightless string. The horizontal force that is required to displace it until the string makes an angle of 45° with the initial vertical direction is

    • Mg left parenthesis square root of 2 minus 1 right parenthesis
    • Mg left parenthesis square root of 2 plus 1 right parenthesis
    • Mg square root of 2
    • fraction numerator Mg over denominator square root of 2 end fraction

    Solution

    A.

    Mg left parenthesis square root of 2 minus 1 right parenthesis straight F calligraphic l space sin space 45 space equals space M g left parenthesis calligraphic l minus calligraphic l space cos space 45 right parenthesis
F space equals space M g left parenthesis square root of 2 minus 1 right parenthesis
    Question 500
    CBSEENPH11020423

    A player caught a cricket ball of mass 150 g moving at a rate of 20 m/s. If the catching process is completed in 0.1 s, the force of the blow exerted by the ball on the hand of the player is equal to

    • 300 N

    • 150 N

    • 30

    • 3 N

    Solution

    C.

    30

    (mv-0)
    ⇒ 0.15 x 20
    F = 3/0.1 = 30 N

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