1. Newton’s Second Law of Motion

2. An unbalanced force acting on an object causes the object to accelerate in the direction of the force.

3. 10/24/2015 copyright 2006 www.brainybetty.com; All Rights Reserved. 3 You might unconsciously know the Second Law. Heavier objects require more force to move the same distance as lighter objects.

4. Wagon moves this way ForceApplied Unbalanced

5. Force, Acceleration, and Mass The greater the force applied to a given object, the greater its acceleration.

6. Force, Acceleration, and Mass For a given force, the greater the mass of an object, the smaller its acceleration and vice-versa.

7. Newton’s Second Law in Real Life Using Newton’s second law of motion, explain why larger trucks usually need more distance to stop than do smaller trucks.

8. Formula for Newton’s Second Law of Motion FORCE = MASS x ACCELERTATION F =force, m= mass, and a =acceleration.

9. What does F = ma say? F = ma basically means that the force of an object comes from its mass and its acceleration. Something very small (low mass) that’s changing speed very quickly (high acceleration), like a bullet, can still have a great force. Something very small changing speed very slowly will have a very weak force. Something very massive (high mass) that’s changing speed very slowly (low acceleration), like a glacier, can still have great force.

10. 10/24/201510 Newton’s second Law con’t. F= M x A Force = Mass x Acceleration the units: -force is measured in Newtons (N) -1 N= 1kg*1 m/s 2 -mass is measured in kilograms (kg)

11. 10/24/2015 copyright 2006 www.brainybetty.com; All Rights Reserved. 11 This is an example of how Newton's Second Law works: Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gas station, and he makes the car go 0.5 m/s 2. Using Newton's Second Law, you can calculate how much force Mike is applying to the car.

12. 10/24/2015 copyright 2006 www.brainybetty.com; All Rights Reserved. 12 F = M x A F= 1000 kg x.5 m/s 2 F= 500 k x m/s 2 So F= 500 N http://www.classzone.com/books/ml_science_com p/page_build.cfm?id=none&mod=13

13. 10/24/2015 copyright 2006 www.brainybetty.com; All Rights Reserved. 13 Examples What force is needed to push a 10kg shopping cart at 3 m/s 2 ? F=m*a F= 10 kg*3 m/s2 F= 30 N

14. Question Identical twins are riding in identical wagons. A friend gives the first wagon a stronger push than the second. Which twin will experience greater acceleration?

15. Question Would a car towing a boat take less, the same, or more time to accelerate than it would without the boat? Explain.

16. Question What will happen to the acceleration of an object if the mass decreases and the force is constant?

17. Question If two identical objects accelerate at the same rate, what must be true of the force applied to each object?