04 Forces

Question 1

Hooke’s Law

Answer 1

Hooke’s Law states that extension (or compression) in a material is directly proportional to the applied force, provided that the limit of proportionality is not exceeded.

Question 2

Upthrust

Answer 2

• Upthrust is the upward force exerted by a fluid on a submerged or floating object.
• It arises due to the difference in pressure between the upper and lower surfaces of the object.

Question 3

Archimedes Principle

Answer 3

Upthrust is equal in magnitude and opposite in direction to the weight of the fluid displaced by a submerged or floating object

Question 4

Principle of Flotation

Answer 4

When an object floats in equilibrium, upthrust is equal to
the weight of the object.

Question 5

Moment

Answer 5

The moment of a force about a pivot is the product of the force and the perpendicular distance from the pivot to line of action of the force.

Question 6

Static equilibrium

Answer 6

A body is in static equilibrium (translational and rotational equilibrium) if

1. net force acting on it is zero
2. net moment about any point is zero

Question 7

3 non-parallel forces acting on an object in equilibrium

Answer 7

For an object in equilibrium acted on by three non-parallel coplanar forces,

1. The vector diagram of the forces must form a closed triangle (for translational equilibrium)
2. The line of action of the forces must pass through a common point (for rotational equilibrium)

Question 8

Principle of Moments

Answer 8

Principle of Moments states that for a body in equilibrium, the sum of clockwise moments about any point is equal to the sum of anti-clockwise moments about the same point