1. 8th Grade Physical Science
Mass, Force and Motion
8th Grade Physical Science

2. S8P3. Students will investigate the relationship between force, mass, and the motion of objects.
Demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia, and friction.

3. What is a force?

4. Calculating Net Forces A net force is the total amount of all forces acting on an object.

5. Add forces moving in the same direction
Add forces moving in the same direction. Subtract forces moving in opposite directions.

6. BALANCED FORCES vs. UNBALANCED FORCES
Balanced forces are always equal to ZERO and DO NOT cause motion.
Unbalanced forces ALWAYS cause motion and NEVER equal to zero.

7. FRICTION is a force that works in the opposite direction to motion.

8. Static Friction vs. Kinetic Friction
Static friction is found where there is NO motion.
Kinetic friction is found where MOTION occurs.

9. Newton’s 1st Law of Motion

10. Newton’s 1st Law of Motion or The Law of Inertia states…
Newton’s 1st Law of Motion or The Law of Inertia states….. An object at rest tends to stay at rest and an object in motion tends to stay in motion unless an unbalanced force acts upon it.

11. Newton’s 2nd Law of Motion

12. More on the Law of Acceleration

13. Newton’s 3nd Law of Motion

14. According to Newton’s 3rd Law of Motion, Forces Always Come In Pairs (or Twos)

15. SI (International System) Units of Measurement We measure forces in NEWTONS. We measure weight in NEWTONS. Weight is measurement of the FORCE of GRAVITY. Gravity is a major force in the universe!

16. S8P5. Students will recognize the characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature.
a. Recognize that every object exerts gravitational force on every other object and that the force exerted depends on how much mass the objects have and how far apart they are.

17. Gravitational Force

18. The Force of Gravity and Mass

19. The Force of Gravity and Distance

20. S8P3. Students will investigate the relationship between force, mass, and the motion of objects.
a. Determine the relationship between velocity and acceleration.

21. Speed and Velocity
Both use the same equation:
Speed or Velocity = distance
time
Velocity has a direction…..Speed does not go in a particular direction.

22. Velocity and Acceleration

23. SI (International System) Units of Measurement We measure speed in m/s
SI (International System) Units of Measurement We measure speed in m/s. We measure velocity in m/s. We measure acceleration in m/s2. (Or…meters per second per second.)

24. S8P3. Students will investigate the relationship between force, mass, and the motion of objects.
c. Demonstrate the effect of simple machines (lever, inclined plane, pulley, wedge, screw, and wheel and axle) on work.