Download Newton`s Laws PPT

GRAVITY
AND MOTION
Bellringer #11
1.
2.
3.
While approaching a red light a semi truck takes longer and uses
more force on the breaks to stop than a small car does. Which of
the following gives reasoning for this situation?
a. The truck is going too fast.
b. The truck has more inertia
c. The truck has more momentum
due to its’ mass.
d. BOTH B and C
While riding the bus to school this morning your bus driver took
a sharp left hand turn. Which direction will your body go?
a. Toward the left
b. Toward the right
c. Toward the back
d. Toward the front
Which of Newton’s 3 laws best explains your reasoning for
question 2?
a. Newton’s 1st law.
b. Newton’s 2nd law.
c. Newton’s 3rd law
Bellringer #13
1.
2.
3.
A penny resting on your elbow wants to remain at rest until an
outside force acts on it. This statement proves that the pennies:
a. Are lazy
b. Have gravity acting on them
c. Have inertia
A bowling ball and a ping pong ball are rolling across the floor.
You notice that the bowling ball is much harder to stop than the
ping pong ball. This is because:
a. The bowling ball has more momentum
b. The ping pong ball has more momentum
c. The bowling ball is bigger
The pop can engine had six holes around the bottom to let water
flow out. What would make the pop can engine move faster
according to Newton’s second law of motion?
a. Less holes in the bottom
b. More holes in the bottom
c. The temperature of the water
Question????
Which object will land sooner
if dropped at the same time,
a ping pong ball or a golf ball?
Acceleration Due To Gravity
Objects fall to the ground at the same rate because
the acceleration due to gravity is the same for all
objects.
The mass of an object does not affect the rate at
which it falls.
ACCELERATING AT A CONSTANT
RATE
All objects accelerate toward Earth at a
rate of 9.8 m/s/s.
WHAT DOES THIS MEAN?
This means that for every second an object falls, the
object’s downward velocity increases by 9.8 m/s.
DOES AIR RESISTANCE AFFECT
FALLING OBJECTS?
Yes!!
THE FORCE OF GRAVITY PULLS OBJECTS
DOWNWARD AS THE FORCE OF AIR
RESISTANCE PUSHES IT UPWARD.
FREE FALL- when an object is being pulled down by gravity,
but no other forces are acting on it.
Does free fall occur with air resistance?
http://www.youtube.com/watch?v=5C5_
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NEWTON’S FIRST LAW OF MOTION
AKA: LAW OF INERTIA
An object at rest remains at rest and an
object in motion remains in motion at constant
speed and in a straight line unless acted on by
an unbalanced force.
Inertia is the tendency of all objects to resist any change
in motion.
Examples:
A golf ball on a tee.
The man will remain in motion
until a force stops his
movement.
NEWTON’S SECOND LAW OF
MOTION
The acceleration of an object depends on the mass
of the object and amount of force applied.
FORCE=MASS X ACCELERATION
Or
a=F/m
How does Newton’s
Second Law explain why
the shuttle’s acceleration
increases during takeoff?
NEWTON’S THIRD LAW OF
MOTION
For every action there is an equal and
opposite reaction.
FORCES ALWAYS ACT IN PAIRS.
The action force is the swimmer’s
hand and feet pushing the water.
The reaction force is the water
pushing on the swimmer’s hands and
feet.
MORE EXAMPLES OF ACTION AND
REACTION FORCE PAIRS
The rabbit’s legs exert a force on
Earth. Earth exerts an equal force
on the rabbit’s legs, causing the
rabbit to accelerate upward.
The shuttle’s thrusters
push the exhaust gases
downward as the gases
push the shuttle upward
with an equal force.
WHAT IS MOMENTUM?
MOMENTUM is a property of a moving object that depends on
the object’s mass and velocity.
Momentum=mass x velocity
THE MORE MOMENTUM AN OBJECT HAS, THE
HARDER IT IS TO STOP THE OBJECT OR
CHANGE ITS DIRECTION.
LET’S
PRACTICE
Explain Newton’s First Law of Motion using
this picture.
A plane will not soar in the air unless it is pushed by the
exhaust from its jet engines.
Newton’s Second Law of Motion
- Which would you have to apply a greater
force to stop and go?
- Which would you rather buy gas for?
- Which would you rather be driving in a
head-on collision?
NEWTON’S THIRD LAW OF MOTION
LIST and DESCRIBE the action and reaction
forces in the following picture.