Forces

Question 1

define centre of gravity

Answer 1

The single point at which the whole weight of a body seems to act on

Question 2

Define Hooke’s Law

Answer 2

Hooke’s Law states that the extension( or compression) of a body is proportional to the applied force, provided that the limit of the proportionality is not exceeded.
(F = kx)

Question 3

Define moment

Answer 3

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

Question 3

Define translational equilibrium

Answer 3

A body is in translational equilibrium the sum of the forces acting on the object in any direction is zero.

Question 4

Define couple

Answer 4

A couple consists of two forces acting on the same body, equal in magnitude but opposite in direction whose line of action do not coincide.

Question 5

Define torque

Answer 5

The torque of a couple is the product of one of the forces and the perpendicular distance between the forces.

Question 6

Define equilibrium

Answer 6

A body is in equilibrium if the sum of forces action on the body in any direction is zero and the sum of moments of the forces action on the body about any point is zero.
(basically reach both translational and rotational equilibrium)

Question 6

Define rotational equilibrium

Answer 6

A body is in rotational equilibrium when there is no resultant torque about any point.

Question 6

Principle of moments

Answer 6

The Principle of Moments states that for an object to be in rotational equilibrium, the sum of clockwise moment about any point must be equal to the sum of anticlockwise moment about that same point.

Question 7

Define pressure

Answer 7

Pressure is the force acting perpendicularly per unit area of a surface

Question 7

Explain upthrust origin

Answer 7

Upthrust arises due to the difference in pressure between the upper and lower surfaces of the object, (partially)submerged in water. The upwards force on bottom surface is greater than the downwards force on top surface, hence, net upwards force is the upthrust.

Question 8

Define upthrust

Answer 8

Upthrust is the net upwards force exerted by a fluid on a submerged or floating object.
( U = ρgv , ρ is density of fluid, v is volume of displaced fluid)

Question 9

Archimedes’ Principle (extra)

Answer 9

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