Power motion

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

Introduction of motion Forces Laws of motion Gravity Velocity Acceleration

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.

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.

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.

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.

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.

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!!!

F = force M = mass A = acceleration

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

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).

Question: A car travels 420 km in 4 hours from Alicante to Madrid. What is its velocity?

Velocity = 105 km/h Alicante-Madrid.

When velocity changes, the word “acceleration” is used.

Acceleration is also a vector. That is, the direction needs to be specified.

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.

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

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.

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.

Introduction of motion Forces Laws of motion Gravity Velocity Acceleration