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Work And Energy Test - 1

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Work And Energy Test - 1
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Weekly Quiz Competition
  • Question 1
    1 / -0

    The work is said to be done, when

    Solution

    Work is done whenever a force acts on a body and the body moves in the direction of the force.

     

  • Question 2
    1 / -0

    Which of the following statements is correct for a freely falling body?

    Solution

    When a body is falling freely, its potential energy is converted into kinetic energy. Therefore, its kinetic energy is increased and potential energy is decreased.

     

  • Question 3
    1 / -0

    What is the angle between displacement and the force applied when the work done is maximum?

    Solution

    Formula used to find the work done is

    Work done (W) = Force (F) × displacement (d) × Cos Ѳ
    When the value of Cos Ѳ is 1, the value of work done is maximum.

    So, Cos Ѳ = 1
    Cos Ѳ = Cos 0 (because Cos 0 = 1)

    Ѳ = 0

     

  • Question 4
    1 / -0

    Which of the following is vector quantity?

    Solution

    They all are scalar quantities.

  • Question 5
    1 / -0

    Which of the following statements is correct?

    Solution

    1. Kinetic energy= ½ m v2 = kgm2/s2

    Potential energy = mgh = kgm2/s2

    So, both the units are same.

    2. Work = F × d = Nm = (kg m / s2) × m = kgm2/s2 (Because 1N = kg m / s2)

    The units of energy are kgm2/s2.

    Therefore, the units of work and energy are the same.

    3. The unit of work is Nm.

     

  • Question 6
    1 / -0

    If an object of mass 1 kg is lifted to a vertical height of 1 m, work done is

    Solution

    Mass of the body (m) = 1 kg

    Acceleration (a) = 9.8 m/s2 (due to gravity)

    Height (Displacement) (d) = 1m

    Now, force = m × a = 1 kg × 9.8 m/s2 = 9.8 N

    Therefore, work done = force (f) × displacement (d) = 9.8 N × 1 m = 9.8 Nm

    Work done = 9.8 J (1J = 1 Nm)

     

  • Question 7
    1 / -0

    A stone of mass m falls from a vertical distance h, the decrease in gravitational potential energy is

    Solution

    Mass of the stone = m
    Vertical distance, i.e. height = h

    Potential energy = mgh
    = mgh

     

  • Question 8
    1 / -0

    Two bodies of equal mass move with uniform velocities of V and 2V, respectively. Find the ratio of their kinetic energies.

    Solution

    Mass of body = m₁ = m Velocity of m₁ = v

    Mass of body = m₂ = m Velocity of m₂ = 2v

    Ratio of kinetic energies = k₁/ k₂= ½ m₁v2 / ½ m₂(2v)2 = ½ mv2 / ½ m4v2 = 1/4

    Therefore, k₁ : k₂ = 1 : 4

     

  • Question 9
    1 / -0

    What must be the velocity (in ms-1) of a moving body of mass 2 kg, which possesses a kinetic energy of 16 J?

    Solution

    Mass of body = 2 kg

    Velocity of body = ? m/s

    Kinetic energy = 16 J = 16 kgm2/s2

    Kinetic energy = ½ mv2

    16 = ½ mv2

    16 = ½ × 2 × v2

    16 = v2

    42 = v2 => V = 4 m/s

     

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