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Chapter4 Dynamics: Newton's Laws of Motion, NG HUI YUN A20SC0187 -…
Chapter4
Dynamics: Newton's Laws of Motion
Newton's First Law of Motion
Every object continues in its state of rest/constant velocity in a straight line, as long as no
net force
acts on it.
only works in inertial reference frames
Law of Inertia
tendency to maintain the state
Mass vs Weight
MASS
measure of inertia of object/quantity of matter
WEIGHT
a force, the pull of gravity acting on object
Newton's Second Law of Motion
Fnet = ma
Force = Rate of Change of Momentum
F = m(v-u)/t
direction of a = direction of Fnet
1N = 1 kg m/s²
Fnet on object at rest on table = 0
contact force/normal force to balance gravitational force
Newton's Third Law of Motion
action-reaction force
Whenever one object exerts a force on a second object, the second object exerts equal force on the first object in opposite direction.
Newton's Law of Universal Gravitational
universal gravitational constant, G = 6.674x10^11 Nm²/kg²
Apparent Weight
force that the object exerts on the scale with which it is in contact
ELEVATOR CASE
AT REST / CONSTANT VELOCITY
Fn-mg=0
Fn=mg = 700N
ACCELERATE UPWARDS
Fn-mg=ma
Fn=m(g+a) > 700N
ACCELERATE DOWNWARDS
Fn-mg=-ma
Fn=m(g-a) < 700N
FREE FALL (a=g)
Fn-mg=-ma
Fn-mg=-mg
Fn= 0N
NG HUI YUN
A20SC0187
