RELATING TO THE PREVIOUS CHAPTER We learnt that:

Force = mass x acceleration Weight is a force, therefore,

Weight = mass x gravitational acceleration

W = mg

ON THE MOON...

Did Buzz Aldrin lose any mass? What does Neil Armstrong mean?

MASS VS. WEIGHT Mass of an

object will be the same no matter where the object is located

Weight of an object will vary according to the gravitational force experienced by the object

Acceleration due to gravity on the moon is one-sixth that of Earth

COMMON MEASUREMENT INSTRUMENTS

Electronic balance

Newton-meter (Spring balance)

Mass Weight

SUMMARYMass Weight

The amount of substance in the body

The force of gravity acting on the body

Constant in any location

Depends on the acceleration due to gravity at the location

Scalar quantity Vector quantity

Measured in kilograms Measured in Newtons

Measured using a beam balance or electronic balance

Measured using a spring balance

INERTIA All bodies with mass possess a

property called inertia The inertia of an object is the

reluctance of the object to change its state of rest, or if it is moving

Consistent with Newton’s first law

INERTIA Force is needed to overcome inertia.

Inertia depends on mass and not weight

The greater the mass, the greater the inertia.

IN A MOVING VEHICLE Sudden braking Round a corner

GRAVITATIONAL FIELD

GRAVITATIONAL FIELD A gravitational field is a region where a

mass experiences a force due to gravitational attraction.

Gravitational field strength, g, is defined as force per unit mass.

GRAVITATIONAL FIELD Near the Earth’s surface, the

gravitational field is uniform The field lines are drawn parallel to

each other

UNITS ANALYSIS Using W = mg,

g = W/mUnits of g is N/kg

Recall free-fallUsing F = maAcceleration due to gravity is 9.8 m/s^2Units of g is also m/s^2