1. acceleration = Force / mass
NOTES 2-3
1. Newton’s 2nd Law of Motion
You’ve observed:
1. a constant force produces an acceleration (direct)
2. acceleration decreases with an increase in mass (indirect)
Newton’s 2nd Law of Motion  a is directly proportional to F and indirectly related to m, and the direction of a is the same as F
Newton (N)  is the SI unit for Force; it is equal to (kg * m/s/s)
acceleration = Force / mass
a = F / m F = m * a m = F / a
Units for acceleration (a) = m/s/s km/h/h
Force (F) = Newton (N)
mass (m) = g kg

2. ***mass must be in kg***
As the result of a serve, a tennis ball (m=58g) accelerates at 430m/s/s for the very brief time in contact with the racket.
What is the force?
Could an identical force accelerate a 5kg bowling ball at the same rate?
***mass must be in kg***

3. 2. Gravity, Mass, Weight, and Newton’s 2nd Law
Newton’s 2nd Law  if there is an acceleration, then there is a force acting on the object
In 2*2 Investigate, the bending ruler was due to the force of gravity 
Gravity accelerates EVERYTHING at 9.8m/s/s
Weight  is the force of gravity acting on an object, where the equation is w = m*g

4. PRACTICE PROBLEMS (EXAMPLES)
1. What does a boy with a mass of 53 kg weigh on Earth?
2. What is the gravitational acceleration on planet X if a 75 kg Astronaut weighs 120 N there?

5. PRACTICE PROBLEMS (EXAMPLES)
1. A tennis racket hits a sand-filled tennis ball (m=275g) with a force of 40N, what is the acceleration?
2. A weightlifter raises a 440kg barbell with an acceleration of 2m/s/s, how much force does the weightlifter exert on the barbell?
3. A mass of 500 kg has a weight of 200 N on Planet X. Is Planet X more massive, less massive or the same mass as Earth? Explain your answer

6. 3. Balanced and Unbalanced Forces
When 2 forces act at the same time, the direction as well as the magnitude of the forces determine the motion of the object
Free-Body Diagram  used to show the relative size and direction of ALL forces acting on an object
BALANCED FORCE= NO ACCELRATION!!!
UNBALANCED FORCE=ACCELERATION!!!!

7. Draw a FBD of a bucket being pulled up at constant speed
Draw a FBD of a bucket being pulled up, acceleration is positive.