Force
Force is the kind of thing which everybody seem to know what it is.
Example: Jedis are the ones that have the force!!!
However, in physics,it has a very precise meaning.
According to Newton's Law: F = ma
We can also give a definition:
Force is something that makes an object (or microscopic particle) move or stop to move. On the absence of forces, the object stays as it is , i. e., either moving at a constant speed or stationary.
The important thing to understand from the definition is that a force is not needed to keep an object moving. You only apply a force if you want to stop it or to accelerate it .
In Newtons own words:
"Every object continues in its state of rest, or of uniform motion in a
straight line, unless it is compelled to change that state by forces
impressed upon it."
Newton's first law of movement
Examples
1) What force is needed to apply to a car , whose mass is 1000 kg, to provide an acceleration of 10 m/s/s ?
F = m a = 1000*10 = 10000 N
2) What is the force of gravity acting in a person whose mass is 50kg?
acceleration of gravity = g = 10 m/s/s
F = 50 * 10 = 500 N
This force is called weight.
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