Forces

Question 1

What is viscous/drag force?

Answer 1

Viscous or drag force is a resistive force that opposes motion of an object through a fluid. e.g. Air resistance

Question 2

Define Hooke’s Law

Answer 2

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

Question 3

Define upthrust

Answer 3

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 4

State Archimedes’ Principle

Answer 4

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

Question 5

State the Principle of Flotation

Answer 5

Principle of Flotation states that when an object floats in equilibrium, upthrust is equal to the weight of the object.

Question 6

Define moment

Answer 6

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

Question 7

Define torque

Answer 7

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

Question 8

State the Principle of Moments

Answer 8

The 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 pivot

Question 9

What is a body in equilibrium?

Answer 9

A body is in equilibrium if the resultant force on the body is zero and the resultant torque on the body is zero.

The first condition means that the body is in translational equilibrium, and that the object is stationary or moving with constant velocity.

The second condition means that the body is in rotational equilibrium and that the body is not rotating or rotating at a constant rate.