Transcript Slide 1
Q: What is Force? • A: Force is anything that causes acceleration. (All accelerations are caused by forces) – Main Principal #4: Objects move, or change motion, because of forces acting upon them! – If an object is stationary, it won’t start moving without a force! – Forces are a “Push” or a “Pull” What we already learned… Makes straight lines on graphs Distance [m] Velocity Tim e [ s] Makes curved lines on graphs Velocity [m] Acceleration 2 Tim e [ s ] So what is the formula for Force? First we had to know the acceleration formula: Velocity [m] Acceleration 2 Tim e [ s ] We have already covered what acceleration is in our last lesson; Q: But what exactly is Mass? Good question! Go to the next slide: Force m ass acceleration [kg m] N 2 [s ] “Newton” (N) is the unit of measurement for Force So a push could be with a force of (for example) 45 N Q: So What is Mass? • A: Mass is the amount of “Matter” – or “stuff” an object has. – “Stuff” is made up of all of the atoms/molecules that make up the object. Objects with mass don’t just suddenly start moving by themselves If it’s already moving, it takes effort to stop it from moving! An object with mass takes some effort to move! Because of the amount of effort It can take to move something, it almost feels like the objects “resists” being moved at all! We call an objects “resistance to change in movement”: “Inertia” So…the more mass something has, the more Thinkforce about “Inertia” like this: is needed to move it! Ok, that the object toinSTART moving. Again,was Inertia for is: an getting objects “resistance to a change” its current motion. But what about stopping when it’s already moving? Aifcar a “heavy” Butcarwith object enough due force What now,is a nice heavy is coming right at YOU? (hard What kind of to force be needed to stop it before runsmove! you over? itswould large amount enough ofpush) mass. it itwill It is quite obvious that is hard to push You have to “overcome” theitinertia a car from for a stationary of the car in order it to moveposition Man Ok, trying this is but I again, heavy! will push harder! Think: what would be required to move the car if it was a much bigger car? Think: what would be required to move the car if it was a much smaller car? Newton’s First Law of Motion: • Also know as: Law of Inertia! – Inertia is an objects resistance to a change in its motion (even if it isn’t moving at all!) – Inertia is caused because objects have mass – The more mass an object has, the more inertia! – “An object at rest will stay at rest unless it is acted upon by an outside force.” (and the opposite is also true! An object in motion will stay in…blah blah blah) What do you think happens to our acceleration w/ different masses? Distance With less mass, it doesn’t take as much effort to get it moving; therefore, I can move it farther in less time (faster). ½ kg 1kg Less Mass = less force needed 2kg With more mass, it takes more effort to get it moving; therefore, it takes me more time to move it farther (slower). Time More Mass = more force needed What do you think happens to our acceleration w/ different masses if we pushed with the same amount of force? Distance Which one of these lines do you think would represent a sports car? SUV, Diesel Truck? The Diesel truck would be the least steep line! Less steep = less velocity!!! Sports car would be the steepest line! Steeper = more velocity!!! The SUV would be the middle line! Steepness of line is in the middle = middle velocity Time