2. In thought  Which of the following do you think would deliver a greater force when colliding with a wall? A golf ball moving at 70 m/s or a baseball moving at 50 m/s? Explain your answer in 3-4 sentences.

3. Objectives  State Newton’s second law of motion and explain how force and mass are related to acceleration

4. Key Term  Newton (N)

5. Newton’s Second Law of Motion  THE NET FORCE ON AN OBJECT IS EQUAL TO THE PRODUCT OF ITS ACCELERATION AND ITS MASS  FORCE = MASS x ACCELERATION  F = ma IMPORTANT

6. F = ma  Acceleration is measured in meters per second per second (m/s 2 )  Mass is measured in kilograms (kg)  Force = kg x m/s 2  One newton (N) is equal to the force required to accelerate one kilogram of mass at one meter per second per second

7. a = F/m  Acceleration of an object can be found if you know the force measured in newtons and the mass of the object  A = F/m  A = m/s 2  F = N  m = kg

8. Force Practice Problem A 52 kg water skier is being pulled by a speedboat. The force causes the skier to accelerate at 2 m/s 2. Calculate the net force that causes this acceleration. F = ma Force = 52 kg x 2 m/s 2 Force = 104 kg x m/s 2 Force = 104 N Force is measured in NEWTONS

9. Force Problems What is the net force on a 2,500-kg elevator accelerating at 2.3 m/s 2 ? Force = 5,750 N What net force is needed to accelerate a 55-kg cart at 17 m/s 2 ? Force = 935 N

10. Changes in Force and Mass  One way to increase acceleration is to increase the force  According to F = ma, when force increases the acceleration also increases  Another way to increase acceleration is change the mass  Mass and acceleration have an inverse relationship, meaning if one goes up the other goes down

11. Review  Force = mass x acceleration  If force increases so does the acceleration  If mass increases acceleration decreases

12. References  Anderson, M. et all (2012) Physical Science. McGraw-Hill: Columbus  Frank, D.V et al (2001). Physical Science. Prentice Hall: New Jersey