These notes are provide detailed information on the forces and motion (Newton's Laws) chapter in the Mind Action Series Physical Science Grade 12 textbook. These notes are colourful, have diagrams for further explanation and are very easily understood.
Force & Motion
Chapter 3
Newton’s First Law Newtons Third Law
An obj continues in a state of rear or
uniform (moving with constant) When object A exerts a force on
velocity unless it is acted upon by a net object B, object B simultaneously
or resultant force exerts an oppositely directed
force of equal magnitude on object
INERTIA: A.
Definition: the property of obj tht
causes it 2 resist a change in its state These forces = action reaction-pair.
of rest / uniform motion Action & reaction cannot add up 2
Object has inertia bcz will x change zero
velocity but bcz unbalanced force acts • Act on diff objs.
on it. Balanced forces can add up 2 zero
Inertia of obj inc w/ inc mass • Act on same object.
Read pg 45&46 examples
Newton’s Second Law Extra note:
When a net force, Fnet, is applied to • Draw separate free body
an object of mass, it accelerates in diagrams for each obj.
the direction of the net force. The • Each diagram normally gets a
acceleration, a, is directly proportional Fnet=ma equation.
to the net force & inversely • Use simultaneous equations 2 find
proportional to the mass missing values (ensure they are
systematic & clear 2 prev loosing
∴if mass = constant ; a ∝ F marks: show steps (sub 1 into 2
1 e.g.)
if force = constant ; a ∝
𝑚 • Tension does not have direction.
Fnet = ma • Always make the direction of
motion (direction of Fapp)
1N force need accel mass of 1kg at positive
1𝑚. 𝑠 −2 • Fnet needs to be a total amount
• Constant V = x Fres on moving obj so if you have forces in opposite
• Constant a = constant Fres on directions you need to subtract
moving obj them.
Acceleration = speed up / slow down / o Example: Fnet (of Fapp
change direction. right & Ff left) = Fapp – Ff
w/e calculating net force add up • Always resolve forces @ an angel
forces in same direction / minus in2 𝜒&𝑦 components.
forces in opposite direction & tk
direction motion as positive.
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