Force and Motion Review. A force is simply a push or a pull . All forces have both size and direction . Do you remember…. BrainPop: Force video clip. NET FORCES. When two or more forces are combined!. Some tips:. Forces in the same direction- add the two forces together.
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When two or more forces are combined!
Remember acceleration involves
It is not just HOW MUCH velocity changes, but it is alsoHOW FAST it changes.
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.
Equal forces in opposite
directions produce no motion
Unequal opposing forces
produce an unbalanced force
(example: driving car on road)
You can reduce friction by adding lubricant to an
Think about adding water to your slide, oil on
your bike chain, wax to your car, furniture polish
to the hardwood floors, ice on the pavement.
How could you increase friction?
Force equals mass times acceleration.
Force = Mass x Acceleration
Newton’s Second Law video clip
If you weighed 70 pounds and your scooter board partner weighed 120, how would this affect your acceleration? What about momentum?
What would happen if the you switched positions?
For every action there is an equal and opposite reaction.
What happens if you are standing on a skateboard or a slippery floor and push against a wall? You slide in the opposite direction (away from the wall), because you pushed on the wall but the wall pushed back on you with equal and opposite force.
Why does it hurt so much when you stub your toe? When your toe exerts a force on a rock, the rock exerts an equal force back on your toe. The harder you hit your toe against it, the more force the rock exerts back on your toe (and the more your toe hurts).
Consider you and the earth
Action: earth pulls on you
Reaction: you pull on earth
Reaction: road pushes on tire
Action: rocket pushes on gases
Newton’s Third Law video clip
Third law – this is equal and opposite reaction.
Third law. This is action-reaction force.
Second law. Force = mass times acceleration.
Second law – it takes a larger force (bulldozer) to push the car
1st law – this is action-reaction
3rd law – this is action – reaction force.
1st Law – this is action-reaction force