The condilion for a lifting machine to be reversible is that its efficiency should be_________________?

Related Mcqs:

1. In a lifting machine with efficiency 60%, an effort of 200 N is required to raise a load of 6 kN. The velocity ratio of the machine is_____________________?

   A. 30
   B. 50
   C. 60
   D. 80

2. In a lifting machine a weight of 5 kN is lifted through 200 mm by an effort of 0.1 kN moving through 15 m. The mechanical advantage and velocity ratio of the machine are respectively_____________________?

   A. 50 and 75
   B. 75 and 50
   C. 75 and 75
   D. 50 and 50

3. A symmetrical body is rotating about its axis of symmetry, its moment of inertia about the axis of rotation being 2 kg -m2 and its rate of rotation 2 revolutions/see. The angular momentum of the body in kg-m2/sec is_____________________?

   A. 4
   B. 6 7i
   C. 8TC
   D. 8

4. If a flywheel increases its speed from 10 rpm to 20 rpm in 10 seconds, then its angular acceleration is_____________________?

   A. —rad/sec 10
   B. —rad/sec 20
   C. —rad/sec 30
   D. none of the above

5. A simple pendulum of length 1 has an energy E when its amplitude is A. If its amplitude is increased to 2 A, the energy becomes____________________?

   A. E
   B. E/2
   C. 2E
   D. 4E

6. A flywheel of moment of inertia 20 kg-m” is acted upon by a tangential force of 5 N at 2 m from its axis, for 3 seconds. The increase in angular velocity in radian persecond is__________________?

   A. 1/2
   B. 3/2
   C. 2
   D. 3

7. A simple pendulum of length / has an energy E, when its amplitude is A. If the length of pendulum is doubled, the energy will be___________________?

   A. E
   B. E/2
   C. 2E
   D. 4E

8. The ratio of kinetic energy and potential energy of a simple harmonic oscillator, at a displacement equal to half its amplitude is given by__________________?

   A. 1:2
   B. 1:1
   C. 2:1
   D. 3:1

9. A disc of mass 4 kg, radius 0.5m and moment of inertia 3 kg-m2 rolls on a horizontal surface so that its center moves with speed 5 m/see. Kinetic energy of the disc is ___________________?

   A. 50 J
   B. 150 J
   C. 200 J
   D. 400 J

10. Two circular discs of same weight and thickness are made from metals having different densities. Which disc will have the larger rotational inertia about its central axis ?

    A. disc with larger density
    B. disc with smaller density
    C. both discs will have same rotational inertia
    D. none of the above