Transcript Newton`s Laws of Motion

Newton’s Laws of Motion
No, not the “fig newton” guy.
…I don’t think…not sure really…
Ok, its possible.
The British scientist Sir Isaac Newton
(1642–1727) was able to state rules that
describe the effects of forces on the
motion of objects
These rules are known as Newton's law's
of motion.
The first law of motion:
“You do not talk about motion!”
Newton's first law of motion states that an
object moving at a constant velocity keeps
moving at that velocity unless an
unbalanced net force acts on it.
If an object is at rest, it stays at rest unless
an unbalanced net force acts on it.
This law is sometimes called the law of
inertia.
Why wear a seatbelt?
Picture yourself in a car that is moving at
25 mph.
– You are not wearing a seatbelt, because
you’re “not going very fast”.
If the car comes to an immediate stop, as it
would during a collision, what will happen
to your body? Will it stop with the car?
What happens in a crash.
The law of inertia can explain what
happens in a car crash.
A car traveling 25 mph during a head on
collision will stop in about 0.1 seconds.
BAM!
Any passenger not wearing a
safety belt continues to move
forward at the same speed the
car was traveling.
Within about 0.02 s (1/50 of a
second) after the car stops,
unbelted passengers slam into
the dashboard, steering wheel,
windshield, or the backs of the
front seats.
Air bags, Crumple zones ect..
Air bags act to increase the time of impact,
reducing the acceleration (and reducing
the force of your body’s impact).
Crumple zones work in the same way:
parts of a car are designed to collaspe
during an impact, increasing the time it
takes to come to a complete stop (they
also ‘absorb’ energy)
Newton’s second law:
Newton’s second law of motion describes
how the forces exerted on an object, its
mass, and its acceleration are related.
Recall that acceleration is the change in
velocity divided by the time it takes for the
change to occur.
So, a hard-thrown ball has a greater
acceleration than a gently thrown ball.
Mass?
Which has more force? A big, heavy ball
or a little ball? Assuming they are
accelerating at the same rate.
Force, mass and acceleration are
related!
Newton’s second law of motion states that
the acceleration of an object is in the same
direction as the net force on the object, and that
the acceleration can be calculated from the
following equation:
Rearrange…
Newtons second law can also be used to
calculate force…
So….