The diagram shows a wheel with a handle. Two forces, F₁ and F₂ of equal magnitudes are acting on the handle as shown in the diagram.

(a) Which force produces negative moment?

(b) Is the wheel in equilibrium? (Yes or No)

(c) Justify your answer stated in (b).

(a) Name the unit of work done, used in subatomic scale.

(b) To which class of lever does a pair of scissors belong?

(c) A stone is tied to a string and displaced from A to B by application of constant force F in three different ways as shown in the diagram below.

Arrange the three cases in ascending order of the work done by the force. (Given AJB is a semi-circle, θ < 90° and AB = 20 m)

To lift a load of 30 kgf, Suhas uses a single fixed pulley while Radha uses a single movable pulley. The displacement of efforts in both the cases are equal. In an ideal situation calculate the ratio of :

(a) the efforts in the two cases.

(b) the potential energy gained by the loads in the two cases.

(c) the efficiencies in the two cases.

(a) One end of a plastic foot ruler is held tightly at the edge of a table and the other end is plucked. Name the vibrations produced in the ruler.

(b) Now the ruler is pushed inside partially and plucked again from its freе end. State with a reason whether the frequency of vibration increases or decreases.