4: Forces

Question 1

Define Hookes Law

Answer 1

F = kx
Hookes Law states that extension or compression of a body is proportional to the applied force, provided that the limit of proportionally is not exceeded.

Question 2

Equation for fluid pressure + proof

Answer 2

Pressure = hpg
proof:
p = F/A = mg/A = pvg/A = hpg (shown)

Question 3

Define Upthrust

Answer 3

Upthrust refers to the upwards force exerted by a fluid on a submerged or floating object.
The upward force arises due the greater pressure at the bottom surface of the object and the lower pressure at the upper surface of the object.

Question 4

Equation for Upthrust

Answer 4

Upthrust = volume fluid displaced x density fluid x g =massfluid displaced x g

Question 5

Define moment

Answer 5

Moment of a force about a pivot is the product of the force and the perpendicular distance between the pivot and the line of action of the force.

Question 6

Define Torque of a Couple

Answer 6

Torque of a couple refers to the product of one of the forces and the perpendicular distance between the forces.

Question 7

Conditions of objects in equilibrium

Answer 7

1. Resultant force is zero
2. Resultant torque is zero

Question 8

Define Principle of Moments

Answer 8

POM states that the sum of anticlockwise moments is equal to sum of clockwise moments about the same pivot