1. Newton’s Second Law and Force Body Diagrams By: Devin Sosnowski, Ryan Kotwica, Craig Reichel, and Jeff Zoellick

2. Terms  net force – the vector sum of all the forces acting on the body  weight – caused by mass accelerating downwards due to gravity  force body diagram – a diagram showing the directions or forces acting on an object.

3. Concepts  Newton’s Second Law of Motion states the acceleration of a body is directly proportional to the force on it and inversely proportional to its mass  This law may be summarized by the equation: a=F/m or more commonly known as… F=ma

4. W Fn Fp Ff Fn W

5. W A Ft W Ff Fn A

6. Examples from the Real World  When you step on the accelerator in a car, you go forward.  When the brakes are applied on a roller coaster, the train of cars slows down and comes to a stop.  A bowling ball will accelerate (roll) faster with more force, but a bowling ball will roll slower than a basketball with the same amount of force because its less massive.

7. Sample Problems  Draw the force diagrams for an object deccelerating due to friction  Draw an object in free fall  Draw an object that’s sliding on an angle with friction  A 5kg bowling ball is accelerating down the lane at 2m/s/s. What is the Net Force?  A 2000 kg pickup truck moves at constant speed of 50 m/s down the street. What is its Net Force?

8. Quiz Type Questions  Accellerations are produced by:  A) Masses  B) Accelerations  C) Velocities  D) Forces  E) Something else!

9. Quiz Type Questions  Accellerations are produced by:  A) Masses  B) Accelerations  C) Velocities  D) Forces  E) Something else!

10. Quiz Type Questions  An object following a straight line path at constant speed _______.  A) must be moving in a vacuum.  B) has no forces acting on it.  C) has a net force acting on it in the direction of motion.  D) has zero acceleration.  E) none of the above.

11. Quiz Type Questions  An object following a straight line path at constant speed _______.  A) must be moving in a vacuum.  B) has no forces acting on it.  C) has a net force acting on it in the direction of motion.  D) has zero acceleration.  E) none of the above.