Download Newton`s Laws of Motion

Newton’s First and Second Laws of Motion
•How and why objects move as they do has fascinated scientists for thousands of
years.
•In the early 1600s, the Italian astronomer ___________________ suggested
that, once an object is in motion, _____________ is needed to keep it
________________.
•Force is needed only to ______________ the motion of an object.
•Galileo's ideas paved the way for ___________________________.
•Newton proposed the ____________________________________________
in the late 1600s.
The First Law of Motion
•Newton’s first law restates Galileo's ideas about ________________________.
•Newton’s first law of motion states that
______________________________________________________________
______________________________________________________________
______________________________________________________________
_____________________________.
•If an object is _________ moving, it will _______________ until a ________
acts on it.
•Clothes on the floor of your room will ________________ unless you pick them
up.
•If an object is _________________________, it will continue to move at a
constant velocity until _____________________________ to change either its
speed or direction.
•For example, a tennis ball flies through the air once you hit is with a racket.
•If your friend doesn’t hit the ball back, the forces of ___________________
_______________________ will eventually stop the ball.
•On Earth, _______________________________ are unbalanced forces that
often change an object’s motion.
Inertia
•Whether an object is moving or not, it _________________any change to its
motion.
•Galileo’s concept of the _______________ to a change in motion is called
________________.
•Inertia is ____________________________________________________.
•Newton’s first law of motion is called the ___________________________.
•Inertia explains many common events, such as why you move _____________in
your seat when a _________________________________.
•When the car stops, inertia keeps you ___________________________.
•A force, such as ___________________________________, it required to
change your motion.
•Some objects have _________________________ than other objects.
•For example, suppose you needed to move an _______ aquarium and an aquarium
_______________________.
•Obviously, the full aquarium is harder to move than the empty one, because it has
_________________________.
•The ___________________________________ of an object, the
_____________________, and the _______________________________ to
change its motion.
•The full aquarium is more difficult to move because it has __________________
than the empty aquarium.
The Second Law of Motion
•Suppose you are baby-sitting two children who love wagon rides.
•Their favorite part is when you ___________________ quickly.
•When you get tired and sit in the wagon, one of the children _______________.
•He soon finds he _______________________________ the wagon nearly as
fast as you can.
•How is the wagon’s acceleration____________ to the ___________ pulling it?
•How is the acceleration __________to the wagon’s __________?
•According to Newton’s second law of motion____________________________
_____________________________________________________________
•This relationship can be written as an equation:
___________________________________________
•Acceleration is measured in meters per second per second ____________, and
mass is measured in kilograms ___________.
•According to Newton’s second law, then, force is measured in kilograms times
meters per second per second _________________________________.
•The short for this unit of force is the ___________________.
•Recall that a newton is the metric unit of ______________.
•You can think of one newton as the force required to give a 1-kg mass an
acceleration of 1 m/s2.
Sample Problem
•A speedboat pulls a 55 kg water skier. The force causes the skier to accelerate at
2.0 m/s2. Calculate the net force that causes this acceleration.
What information are you given?
–Mass of water skier =
–
Acceleration of the water skier =
What quantity are you trying to calculate?
–The net force
–What formula will you use?
•Acceleration = Net force ÷ mass
•OR Net Force = mass x acceleration
•Perform the calculation
–Fnet = m x a
–F =
–F =
–F =
x
kg x m/s2
Practice Problems
•What is the net force on a 1,000 kg object accelerating at 3 m/s2?
•What net force is needed to accelerate a 25 kg cart at 14 m/s2?
Changes in Force and Mass
•How can you _______________________________________ of the wagon?
•Look again at the equation.
•One way to increase acceleration is by ______________________________.
•If the _________ is _______________, acceleration and ___________
change in the same way.
•So to increase the acceleration of the wagon, you can
_________________________________________ used to pull it.
•Another way to increase acceleration is to _______________________.
•According to the equation, acceleration and _________change in
___________________________________.
•If the ____________________________, an increase in ___________ causes
a ___________________________________________.
•The opposite is also true: A _______________________________ causes an
____________________________________ with a constant ____________.
•To increase the acceleration of the wagon, you can _____________________.
•So instead of you, the children should _____________________________.
•Look at the pictures on the right.
•Which vehicle do you think would
require a greater force to push?
___________________________
•Why do you think this?
____________________________
____________________________
____________________________
•Using the equation, solve for the
amount of force.
____________________________
____________________________