Chapter 4: Forces

Question 1

State Hooke’s Law

Answer 1

Hooke’s law states that the extension or compression of a body is proportional to its spring constant provided that the limit of proportionality is not exceeded.
F = kx

Question 2

Define upthrust

Answer 2

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

Question 3

State Archimedes principle

Answer 3

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

Question 4

State the Principle of Floatation

Answer 4

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

Question 5

Define moment/torque

Answer 5

The moment/torque of a point is the product of the force and the perpendicular distance from the line of action to that point.

Question 6

Define torque of a couple

Answer 6

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

Question 7

Define equilibrium (forces)

Answer 7

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

Translational equilibrium:
Sum F = 0

Rotational equilibrium:
Sum t = 0

Question 8

Principle of moments

Answer 8

The principle of moments states that for a body in equilibrium, the total clockwise moments about any point is equal to the total anticlockwise moments about the same point.

Question 9

Formula for EPE

Answer 9

E = 1/2(k)(x)^2

Question 10

Formula for fluid pressure

Answer 10

p = hpg