Page 76 - text book form physics kssm 2020

2.8 Weight

Photograph 2.11 shows a man lifting a barbell.
Earth’s gravitational pull acting on the barbell
contributes to the weight of the barbell. The weight
of the barbell makes it difficult for the man to lift it.
The barbell will drop to the ground with an
acceleration if the man releases it. According to
Newton’s Second Law of Motion,
Photograph 2.11 Lifting a barbell
F = ma
• Gravitational force acting on the barbell is its weight, W.
• Acceleration of the barbell is gravitational acceleration, g.
W = mg

Weight is a vector quantity W = mg
which has the same W
direction with gravitational Unit for weight: N g = m
force, that is towards the Unit for mass: kg –1
centre of Earth. Unit for g: N kg

–1
Physical quantity, g with unit N kg is the gravitational field strength. Gravitational field
strength, g is the force acting per unit mass caused by gravitational pull. For objects on the surface
of the Earth, gravitational field strength, g is 9.81 N kg . Each 1 kg mass experiences a force of
–1
gravity of 9.81 N. Can you calculate your weight on the surface of the Earth?
Photograph 2.12 shows an astronaut wearing a full spacesuit when exploring the Moon. It is
easier for the astronaut to walk on the Moon compared to walking on Earth. Why is this so?

Astronaut’s movements on
the Moon

http://bt.sasbadi.com/p4070

M
Malaysiakualaysiaku
MY PRIDE
Dato. Dr. Sheikh Muszaphar
Photograph 2.12 Astronaut wearing a Shukor bin Sheikh Mustapha
full spacesuit on the Moon is the first astronaut of Malaysia.

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2.8.1