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NDA - Law of motion Test 1324
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NDA - Law of motion Test 1324
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  • Question 1/5
    1 / -0.33
    A tennis ball is thrown in the vertically upward direction and the ball attains a maximum height of 20 m. The ball was thrown approximately with an upward velocity of
    Solutions

     To calculate the initial velocity of the object with which it is thrown upward, we can use kinematic equation as follows,

    =

    Here, v is the final velocity,

    U is the initial velocity,

    G is the acceleration due to gravity

    H is the height attained by the object.

    We know that at the maximum height, the velocity of the object becomes zero. Therefore, we can substitute 0 for v in the above equation.

    =

    =

    u=

    Substituting 9.8 for g and 20m for h in the above equation, we get,

    u== 19.8m/s20m/s. Hence, the correct answer is D

  • Question 2/5
    1 / -0.33
    A bullet of mass 30g travelling with a velocity of 400 m/s penetrates 8 cm into a wooden block. The force exerted will be
    Solutions

    The initial velocity of the bullet u = 400 m/s

    Final velocity v = 0 m/s

    Distance at which it comes to rest s = 8 cm = 0.08 m

    Mass of bullet m = 30 gm = 0.03 kg

    We have to find the force exerted.

    First we will find the acceleration of the bullet when it penetrates

    Using 3rd equation of motion,

    To find the force we will use the relation

  • Question 3/5
    1 / -0.33
    Which one of the following statements about speed and velocity is correct?
    Solutions

    Speed is a scalar quantity as it has only magnitude and no direction, it changes when only their magnitude is changed while velocity has both magnitude and direction thus it is called a vector quantity. Vector quantity change when either their magnitude change, direction change or both.

    Hence the correct option is D.

  • Question 4/5
    1 / -0.33
    A bullet of mass 50 gm is fired from a gun of mass 1.5 kg. The recoil velocity of the gun is 5 m/s. Find the velocity of the muzzle.
    Solutions

    The mass of the bullet m = 50 gm = 0.05 kg

    Mass of the gun M = 1.5 kg

    Recoil velocity V = 5m/s

    We have to find the muzzle velocity v.

    Using conservation of linear momentum

    The muzzle velocity is 150 m/s.

    Hence A is the correct option.

  • Question 5/5
    1 / -0.33
    How much force has to be applied for the greater rate of change in momentum vector?
    Solutions

     Momentum of a body is the product of mass and velocity of that body. Force is directly proportional to the rate of change of momentum and the change in momentum takes place in the direction of the force.

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