Transcript File

Newton’s 1st and
Laws
nd
2
Newton
 In
the 1660’s Sir
Isaac Newton
formulated three
laws of motion.
 These laws
describe how
forces affect
motion.
 All by the age of 18
Newton’s
 An
st
1
Law
object at rest
stays at rest and an
object in motion
stays in motion until
acted on by an
outside force.
 Nothing will begin
moving or stop
moving unless
something makes
it.
Inertia and the
 Inertia
is the
property of an
object that causes
it to resist motion.
 The more mass
an object has, the
more inertia it
has.
st
1
Law
Newton’s 2nd Law
2nd law is Force =
mass times
acceleration.
 F=ma
 Large force on a
small mass gives
large acceleration.
 Small force on a large
mass gives small
acceleration
 The
A Newton
 The
unit of force is
called a Newton
(N).
 1N will accelerate
1kg at 1m/s2
 After any force
answer always put
N for the units.
Practice with the
A
car has a mass of
1000 kg and is
accelerating at 3m/s2.
What is the force acting
on the car?
 What force is need to
cause a 3kg bowling
ball to accelerate
4m/s2?
nd
2
Law
Newton’s
 For
rd
3
Law
every action there is
an equal and opposite
reaction.
 Ex. Sitting in your chair.
Gravity pulls you down
and your chair pushes
back with an equal and
opposite force.
Rockets
 The
action: Fuel
is forced out of
the back of the
rocket.
 The reaction:
The rocket is
moved forward.
Momentum
 All
moving
objects have
momentum.
 Momentum
depends on the
mass and
velocity (speed)
of an object.
Calculating Momentum
 Momentum
= mass x velocity
Momentum(P) = m x v
 Mass is measured in kg and
velocity in m/s. Therefore the
units of momentum are kg-m/s.
 This is said kilogram meters per
second.
Practice with Momentum
A
bowling ball has a
mass of 3 kg and
travels with a velocity
of 5 m/s. What is the
momentum?
 A car weighing 1500
kg is traveling with a
velocity of 4 m/s.
What is the
momentum?
Conservation of Momentum
 The
total
momentum is
always conserved
unless acted on
by an outside
force.
 Momentum is
transferred from
one object to
another.
Examples of Conservation
A
bat hitting a
baseball. The
momentum is
transferred from the
bat to the ball.
 Bowling. The
momentum is
transferred from the
bowling ball to the
pins.