Transcript newton`s laws of motion - Ms Cole Science 2012-13

NEWTON’S LAWS OF MOTION
Newton’s Laws
Newton’s Laws are all about force and
motion.
 Force is a push or pull; something
that changes the motion of an
object

Types of force
Gravity: Force of attraction
between two masses.
 Friction: Force that resists motion
between two surfaces.

Balanced and unbalanced forces

If the net force on an object is zero, the
forces acting on the object are balanced.
Overall force acting on an object when
forces are combined is the net force.
 An Unbalanced Force produces an
non-zero net force, which changes
the object’s motion.

Newton’s 1st Law

Newton’s 1st Law: An object at rest
will remain at rest, and an object in
motion will remain in motion with
the same velocity unless an
unbalanced force acts upon it.
Newton’s 1st Law

Anytime you read about a situation
where something is at rest and then it
starts moving or is moving and then it
stops, it is talking about Newton’s 1st Law.
Newton’s 1st Law

There is a box that is sitting on the floor
at rest. It will remain at rest until
somebody pushes it.
At rest…
In motion…
Newton’s 1st Law

You are driving in a car with no seat belt on. You see a family of
ducks and slam on your brakes to avoid hitting them. Since you are
not wearing your seat belt, you fly out of the car (remain in
motion) until you hit the ground (an unbalanced force).
AHH
!
Ouch
In motion…
At rest…
Inertia (ih-NER-shuh)
Inertia is the resistance of an object
to a change in the speed or direction
of its motion.
 How does this apply to Newton’s 1st law?

◦ The first law describes the tendency of
objects to resist changes in motion.
◦ AKA they’re one in the same.
Newton’s Second Law
 Newton’s
Second Law states
that the acceleration of an object
increases with increased force
and decreases with with
increased mass.
 Force = mass x acceleration
Newton’s 2nd Law—Apply the
Knowledge

What force is needed to accelerate a 10 kg
shopping cart 3 m/s2?
Force = mass x acceleration
 Mass = 10 kg, Acceleration =3 m/s2
 F= 10 kg x 3 m/s2
 Answer: F=30 N

CFU
What force is needed to accelerate a 20 kg
boulder to 2 m/s2?
 Force = mass x acceleration
 Mass = 20 kg, Acceleration =2 m/s2
 F= 20 kg x 2 m/s2
 Answer: F=40 N

PRACTICE QUESTIONS (complete
on your handout)

A 10 kg bowling ball would require what
force to accelerate down an alleyway at a
rate of 3 m/s2?
PRACTICE QUESTIONS (complete
on your handout)

Victor has a car that accelerates at 5 m/s2.
If the car has a mass of 1000 kg, how
much force does the car produce?
Newton’s Third Law—in more
simple terms
 Sometimes
referred to as law of “EQUAL
and OPPOSITE”
 For every reaction, there is an “equal and
opposite” reaction
 What ever happens, there is an exact (but
opposite) force that happens as well.
CFU…
 So
if Nixon pushes against a
wall with a force of 25N, how
much force does the wall
exert on him, and in what
direction?
 25 N
Action-Reaction Pairs
 The
force that is exerted on an object and
the force that exerts back are known as
action-reaction pairs.

Example: When Abed bangs his toe into the leg of the
table, the same amount of force he exerts on the table is
exerted back on his toe.
Click the link below to sum up
Newton’s Laws of Motion

http://www.d123.org/olhms/dedie/docume
nts/2-3Forces.pdf