Material para el profesorado de Ciencias Naturales

1. Online source: http://www.physics4kids.com/files/motion_intro.html

2.  Introduction of motion
 Forces
 Laws of motion
 Gravity
 Velocity
 Acceleration

3.  Everything in the universe moves.
 Question: if you are sitting still at your
desk, are you moving?
 Answer: Yes. You are on Earth. The Earth
is moving around the Sun. The Sun is
moving around our galaxy.

4.  Forces need to act upon an object to
get it moving or to change its motion.
 Forces could be big or small.
 Big forces: the pull of a star on a planet
 Small forces: the pull of a nucleus on an
electron.

5.  Scientists measure forces in units called
Newtons (N).
 Example: you kick a soccer ball with a
force equivalent to 12 N. The force of
gravity causes the ball to return to the
surface.

6.  Gravity or
gravitational forces
are forces of
attraction.
 Every object in the
universe that has
mass exerts a
gravitational pull, or
force, on every other
mass.

7.  Sir Isaac Newton came up with the three
basic ideas that are applied to the physics of
most motion.
 Scientists now call them Newton's Three Laws
of Motion.

8.  An object at rest tends
to stay at rest, and an
object in motion tends
to stay in motion, unless
acted upon by an
unbalanced force.
 That is, objects tends to
keep on doing what
they're doing!!!

9.  F = force
 M = mass
 A = acceleration

11.  The third law says
that for every action
(force) there is an
equal and opposite
reaction (force).
Forces are found in
pairs!

12.  Velocity is word used describe if a
motion is fast or slow. That is, velocity is
the rate of motion in a specific direction.
 Question: if you are walking 5 km/hour.
Would you say that you know your
velocity?
 Answer: No. You only know your walking
speed. Your velocity would be if you are
walking 5 km/hour north (or S/W/E).

13.  Question: A car
travels 420 km in 4
hours from Alicante
to Madrid. What is its
velocity?
 Velocity = 105 km/h
Alicante-Madrid.

14.  When velocity changes, the word
“acceleration” is used.
 Acceleration is also a vector. That is, the
direction needs to be specified.

15.  There are a few
special situations
where acceleration
may be constant.
This type of
acceleration
happens when there
is a constant net
force applied. The
best example is
gravity.

16.  The acceleration of an object due to
gravity is constant near the Earth´s
surface. Do you know its general value?
 G = 9.82 m/s2

17.  In a vacuum (el vacío), which
would fall faster: a feather or a ball
of the same mass?
 Answer: they would fall at the
same rate in a vacuum.
 Note: in real life, there is air all
around us. When a feather falls, it
falls slowly because the air is in its
way. There is a lot of air resistance
and that resistance makes the
feather move slower.

18.  Do you think that gravities (or gravitational
forces) on other planets are the same on
Earth?
 The gravities of other planets are different
from Earth's gravity because they may have
different masses and/or sizes. Even though
the gravity may be smaller or larger, it will
still create a constant acceleration near the
surface of each planet.

19.  Introduction of motion
 Forces
 Laws of motion
 Gravity
 Velocity
 Acceleration