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# Forces and Motion

This is a middle school presentation on Forces & Motion.
by

## Roberto Crespo

on 8 April 2014

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#### Transcript of Forces and Motion

Inertia
Inertia is the tendency for an object to resist a change in motion.
That means that an object that is still will resist moving and an object that is moving will resist stopping.
Gravity and Friction
Gravity is the force that attracts ALL objects towards one another.
The sum of all of the forces acting on an object is called the net force
Balancing Forces
Understanding Friction:
A friction force is a resistive force acting in the opposite direction when the object is tending to move or when already in motion.
Sliding friction comes into play when the object is in motion, it is also called "Kinetic Friction".
Static friction comes into play when the object is a rest (stationary) and tending to move.
A force is a push or pull.
Force
Forces & Motion
Force Equations
F = Force
a = acceleration
m = mass
F = ma
a = F/m
m = F/a
The unit for force is Newtons.
The abbreviation for Newtons is "N".
Example: Joey threw the baseball with a force of 5N.
The more mass an object has, the more inertia it has.
That means that bigger objects resist moving or stopping more than little objects do.
On Earth, the acceleration of falling objects due to gravity it 9.8 m/s
2
Friction is a force that acts between two substances that touch each other.
A balanced force occurs when the net forces acting on an object cancel out or equal zero.
An unbalance force occurs when the net forces acting on an object do not equal zero. Motion only takes place in this scenario.
Speedquan pulls with 50N of force.
Velocishawn pulls in the opposite direction with the same amount of force, 50N.
Their net force is zero. They have a balanced force.
Team Twofokes pulls with a force of 60N.
Team FoFolks pulls with a force of 130N in the opposite direction
The net force of the tug-o-war is 70N because 60N on each side cancel out and you have 70N in the right direction remaining from team Fofolks.
When two forces act in the
together.
5N
+ 10N =
15N
The sum of all the forces acting on an object is known as the net force.
When two forces act in opposite directions, you subtract.
5N
- 10N =
-5N
An unbalanced force acting on an object can change its speed, or direction of motion, or both.
If you exert the same force on two objects of different mass, you will get different accelerations (changes in motion). The effect (acceleration) on the smaller mass will be greater (more noticeable).
For example: The effect of a 10 newton force on a baseball would be much greater than that same force acting on a truck. The difference in effect (acceleration) is entirely due to the difference in their masses.
Understanding Force:
THE END!
Full transcript