Transcript MOTION and FORCES

MOTION and FORCES
The process of change of position
as it relates to some seen or unseen
push or pull on an object.
Newton’s Three (3) Laws
of Motion
 INERTIA
 ACCELERATION
 REACTIONARY FORCES
INERTIA
 An object at rest will remain at rest or an
object in motion will remain in motion
unless acted upon by some outside
force.
Example: Riding in a car and then
suddenly apply the brakes; your body
continues to move forward.
ACCELERATION
 An object of a certain size and MASS will
accelerate depending on the size of the
FORCE acting upon it and the
DIRECTION in which it acts.
Example: A TRACTOR TRAILER TRUCK
and a VOLKSWAGON CAR with a
DEISEL ENGINE and 4 CYLINDER
ENGINE going UPHILL or DOWNHILL.
REACTIONARY FORCES
 For every Action there is an equal and opposite
Reaction.
Example: Fill a balloon with air, let the balloon go
and allow for the air to escape to observe the
balloon’s movement.
Definitions
 Speed- how fast an object moves.
 Velocity- how fast an object moves, with
specific reference to DIRECTION.
 Acceleration- how Speed/Velocity
changes with time (a change in speed).
 Force- any push or pull on an object.
 Momentum- an objects mass multiplied
by it’s Velocity.
FORMULAS
Speed = Distance/Time
S=D/T
Acceleration=Velocity(final)-Velocity(initial)
Time
Momentum = Mass X Velocity
Force = Mass X Acceleration
Units of Motion
 SPEED – m/s, mph, km/hr etc.
 ACCELERATION – m/s² or km/hr/sec
Constant for acceleration due to GRAVITY.
g = 9.8 m/s²
 MOMENTUM – kg x m/s
Sample Motion Problems
1. Calculate the speed of a runner that ran 55m
in 5.5sec. ___________________
2. What is the velocity of a car that traveled
150km N in 3hrs? __________
3. How fast does a Porsche accelerate from a
standstill in 10sec to a top speed of
120km/hr?_____________________
USE THE TRIANGLE TO WORK PROBLEMS!!!
ADARA Says: Hi!
VECTORS
 Vectors is a way of representing the
magnitude and direction of velocities,
forces, etc. with the use of arrows.
 Resultant Vector is found when you
either use the Pythagorean Theorem for
vectors at right angles to each other or
use graphical addition.
PYTHAGOREAN THEOREM
 In order to find the length of a resultant
vector where two vectors are at right
angles to one another you must use the
following formula:
a² + b² = c²
(See sample problems worked by teacher)
Graphical Addition
 Another method for addition of vectors is
to manipulate their graphical
representations on paper. A ruler is
needed to draw the vectors to the correct
length. A protractor is needed to insure
the correct angles. The length of the
arrows should be proportional to the
magnitude of the quantity represented.
Rules to Remember
 When drawing vectors, always use a
straight edge.
 Vectors should always be TIP to TAIL.
 All vector lengths should be proportional
to the magnitude of the quantity.
 BE ACCURATE, ACCURATE,
ACCURATE!
FORCE
 A FORCE is any push or pull on an object.
 BALANCED FORCES occur when two or more
forces act in different directions on an object
and the NET FORCE is ZERO.
 UNBALANCED FORCES occur when two or
more forces act in different directions on an
object and a NET FORCE occurs in the
direction of the larger force.
TYPES of FORCES
 FRICTIONAL FORCE- is the resistance
of motion of an object.
 GRAVITATIONAL FORCE- is the
attraction between two objects that is
determined by the size and distance of
the objects.
 CENTRIPETAL FORCE- the force
exerted on an object in a circular motion.
FORCE FORMULA
 Force = Mass X Acceleration
F = ma
Unit of Force is the NEWTON. This is an
abbreviation for kg x m/s².
Acceleration of a falling object due to
GRAVITY is called g.
The constant for g = 9.8m/s²
Sample Problem
 What is the force of a 250 kg linebacker
that hits a dummy at an acceleration of 5
m/s² ?
To solve:
F=?
F=ma = (250kg)(5m/s²)
M=250kg
= 1250N
A=5m/s²
Universal Law of
Gravitation
 Every object in the Universe pulls on
every other object.
 The more mass an object has, the
greater it’s gravitational force (pull).
 The greater the distance between two
objects, the less attraction they have for
each other.
Inverse Square Law
 This is the relationship between
gravitational force proportional to the
inverse square of the distance between
the objects. Simply put, the Gravitational
Force increases with increased Mass and
decreases as the distance between the
masses becomes greater.
Weight vs Mass
 Gravity gives the MASS of an object it’s
WEIGHT.
 Mass measures the amount of matter in
an object.
 Weight is a force that changes
depending on the amount of gravity
pulling on an object.