Gravity and Weight

As seen previously, weight is different from:

Mass

Mass:

An Intrinsic property of matter, whereas weight is force exerted on an object due to gravity

The downward pull that the Earth exerts on bodies outside of itself:

Is a specific case of gravity at work

Weight can easily be measured using:

A spring scale like that found in many people’s bathrooms

The direction of weight for all objects on earth:

Is the same, straight down toward the center of the earth

The general formula for Newton’s Law of Universal Gravitation can be used to explain why:

The same person will weigh less on planets of different masses and sizes

When astronauts walked the moon:

Their weight was only 1/6 of what it was while on earth

Unless you are told otherwise, it is safe to assume that for the purposes of everyday mechanical work:

The location is here on Earth

For bodies free falling near the Earths surface:

The acceleration due to gravity is calculated to be about 9.8 m/s, ignoring air resistance

“Near the Earth’s surface” really means:

Anywhere on Earth, including on top of Mount Everest or parachuting from a plane thousands of meters in the air

The value of g doesn’t change:

Significantly at the top of a stair ladder

W=MG is:

A modified version of Newton’s Second Law

W is weight in:

Newtons

M is Mass in:

Kilograms

G is acceleration due to:

Gravity( either m/s² or N/kg)

To determine an objects weight in N, therefore:

Simplify multiply its mass in kg by 9.8