physic chapter 1.5

what can forces do to objects

change shape,size,direction,stretch

how to do hookes law experiment

fix spring securely on clamp stand next to vertical ruler. record unextended length. add know load and record extension of spring. stretched-original. repeat with different masses.

what is limit of proportionality

point on the graph where the line stops being straight and curves because hookes law is no longer obeyed

what is spring constant

force per unit extension. force/extension

what is newtons first law

object remains at rest or moves at constant speed unless acted upon by a resultant force

what is Newton second law

A resultant force changes an object's velocity by altering its speed or direction. f=ma. always in same direction.

what if force increases in object in circular motion (mass and radius constant)

speed increases

what if force increases in object in circular motion (speed and mass constant)

radius decreases

what is solid friction

force between two solid surfaces touching each other that converts kinetic to thermal

what is drag

friction on an object moving through liquid or gas. drag increases as speed increases.

what is moment

measure of an forces turning effect around an pivot

moment formula

$\text{Moment} = \text{force} \times \text{perpendicular distance from the pivot}$ in nm

what is the principle of moments

When an object is in equilibrium, the sum of clockwise moments about any point equals the sum of anticlockwise moments about that same point.

when is an object in equilibrium

no resultant force and no resultant moment

what is centre of gravity

imaginary point through which entire weight of object acts on

how to find centre of gravity

• Make a small hole near the edge of the flat, irregular object (lamina).

• Hang the lamina freely from a pin or nail acting as a pivot.

• Hang a plumb line (string with a heavy weight) from the same pin and draw a straight vertical line down the lamina following the string.

• Repeat the process by hanging the lamina from a different corner.

• The centre of gravity is located precisely at the point where all the drawn lines intersect.

when is object stable

An object is stable if its centre of gravity is low and the vertical line drawn downwards from its centre of gravity falls within its base area.