Summary Forces and Motion Physics Exam General Simplified Notes 1
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Module
Physics
Institution
Physics
Physics Exam General Notes
1: Forces and Motion
● Kinematics: study of motion
● Basic types of motion:
o Uniform (constant speed in straight line)
o Non-uniform
● Scalar quantity: with magnitude & no direction
o Distance, average speed
● Vector quantity: with magnitude (arrow above ...
1: Forces and Motion
● Kinematics: study of motion
● Basic types of motion:
o Uniform (constant speed in straight line)
o Non-uniform
● Scalar quantity: with magnitude & no direction
o Distance, average speed
● Vector quantity: with magnitude (arrow above it) & direction (in square brackets after unit)
o Position, displacement, acceleration
● Velocity:
o Rate of change of position
o Average velocity: displacement divided by time interval for that change
o 2-D motion: using GPS (global position system)
▪ N/S/E/W to communicate directions
▪ Ex: 5.0 cm [25° S of E] or [E25°S]
● Acceleration: rate of change of velocity
● V-t graph to find other things:
o Area under line gives displacement, slope gives acceleration
● Resultant displacement of 2 dimensions:
o Vector sum of individual displacements
o Use Pythagorean Theorem and SOH-CAH-TOA
● Relative motion: velocity of a body relative to a particular frame of reference
● Methods of writing direction:
o GPS = [E25°S] or [25° S of E]
o Bearing = [N 160°] (measure CW from North position)
2: Energy
● Dynamics: causes of motion
● Force: push or pull, vector quantity
o 4 fundamental forces: gravitational, electromagnetic, strong nuclear, weak nuclear
● Unit of force: Newton (N) -> 1N = 1(kg x m)/s2
● Net force/resultant force: vector sum of all forces acting on an object
● Mass: quantity of matter in an object (standard: kg)
● Weight: force of gravity on an object (Fg), measured in Newton’s
Newton’s Laws of Motion:
, 1. If the net force acting on an object is zero, the object will maintain its state of rest or constant
velocity.
2. If the external net force on an object is not zero, the object will accelerate in the direction of that
net force. The magnitude of the acceleration is proportional to the magnitude of the net force
and inversely proportional to the object’s mass.
3. For every action force, there is a reaction force equal in magnitude but opposite in direction.
o Law of Universal Gravitation: Force of gravitational attraction between any two objects is
directly proportional to the product of the masses of the two objects, and inversely
proportional to the square of the distances between their centres.
Friction:
● Static friction (Fs): force that tends to prevent a stationary object from starting to move
o Starting Friction: max static friction, amount of force to overcome to get object to move
● Kinetic friction (FK): force that acts against an object’s motion in a direction opposite of the
direction of motion
o Sliding friction, rolling friction, fluid friction
● Coefficient of friction (µ): number that indicates the ratio of the magnitude of the force of
friction (Ff) between 2 surfaces to the magnitude of the force perpendicular to these surfaces
o µK for FK, µs for Fs; larger means more friction
Energy:
● Energy: capacity to do work
o 1 J (joule) = 1 Nm = 1(kg x m2)/s2
o Forms: thermal, electrical, radiant, nuclear potential, gravitational potential, kinetic,
elastic potential, sound, chemical potential
● Work: energy transferred to an object by an applied force over a measured distance
o Power: rate of doing work or transforming energy
▪ 1 W = 1 J/s
● Gravitational potential energy: energy possessed by an object because of its position relative to
a lower position
● Kinetic energy: energy possessed by an object due to its motion
● Law of Conservation of Energy: energy cannot be created nor destroyed. When energy changes
from one from to another, no energy is lost.
o Valley problems, pendulum problems, objects dropped from a height
▪ (mvA2)/2 + mghA = (mvB2)/2 + mghB
o Ramp problems
▪ Moving up: (F – Ff) ∆d = mgh
▪ Moving down: mgh – Ff∆d = ½mv2
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