Section A: Short Answer Questions
Define moment of force and state its S.I. unit. (1)
State the condition when, on applying a force, a body has: (2)
(a) Translational motion
(b) Rotational motion
Classify the following among contact and non-contact forces: (5)
(a) Frictional force
(b) Normal reaction force
(c) Force of tension in a string
(d) Gravitational force
(e) Electrostatic force
(f) Magnetic force
Section B: Numerical Problems. (6)
A half-meter rod is pivoted at the center with two weights of 20 gf and 12 gf suspended at distances of 6 cm and 10 cm from the pivot, respectively:
(i) Which of the two forces acting on the rod causes a clockwise moment?
(ii) Is the rod in equilibrium?
(iii) If the direction of the 20 gf force is reversed, what is the magnitude of the resultant moment of force on the rod?
A uniform meter rule is balanced at its midpoint. If a weight of 50 gf is suspended at the 10 cm mark, where should a weight of 100 gf be suspended to balance the rule again?
A force of 10 N is applied perpendicular to a wrench at a distance of 0.25 m from the nut. Calculate the moment of force applied.
Section C: Conceptual Questions(10)
Explain why the moment of a force is considered a vector quantity.
Describe the principle of moments and its application in daily life.
Differentiate between center of mass and center of gravity.
Why is it easier to open a door by applying force at the edge farthest from the hinges rather than near the hinges?
Section D: Application-Based Questions(10)
A seesaw is balanced with a child weighing 30 kg sitting 2 meters from the pivot on one side. How far from the pivot should a 40 kg child sit on the other side to balance the seesaw
Explain how the design of a spanner (wrench) makes use of the concept of moments to tighten or loosen bolts effectively.
Discuss the role of the center of gravity in the stability of vehicles.
How does increasing the length of a lever arm affect the mechanical advantage? Provide a practical example.
A ladder is leaning against a wall making an angle with the ground. Explain the forces acting on the ladder and the conditions for its equilibrium.
Section E: Multiple Choice Questions
Which of the following does not affect the moment of a force about a point?
(a) Magnitude of the force
(b) Distance from the point
(c) Direction of the force
(d) The point about which moment is calculated
The S.I. unit of moment of force is:
(a) Newton
(b) Newton-meter
(c) Joule
(d) Pascal
A couple produces:
(a) Purely translational motion
(b) Purely rotational motion
(c) Both translational and rotational motion
(d) No motion
If the perpendicular distance between the line of action of a force and the pivot is doubled, the moment of the force:
(a) Remains the same
(b) Is doubled
(c) Is halved
(d) Is quadrupled
The center of gravity of a uniform circular disc lies:
(a) At the center of the disc
(b) On the circumference
(c) At any point on the disc
(d) Outside the disc
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