大象传媒

Weight, mass and gravitational field strength

The of an object may be thought of as acting at a single point called its . Depending on the object's shape, its centre of mass can be inside or outside it.

The weight of an object and its mass are directly proportional. For a given gravitational field strength, the greater the mass of the object, the greater its weight.

weight = mass 脳 gravitational field strength

\(W = m~g\)

This is when:

  • weight (W) is measured in newtons (N)
  • mass (m) is measured in kilograms (kg)
  • gravitational field strength (g) is measured in newtons per kilogram (N/kg)

Example

An apple has a mass of 100 g. Calculate its weight on Earth (g = 9.8 N/kg).

\(100~g = \frac{100}{1000} = 0.1~kg\)

\(W = m~g\)

\(W = 0.1~kg \times 9.8~N/kg\)

\(W = 0.98~N\)

Question

Calculate the weight of a 30 kg dog (g = 9.8 N/kg).