3. balanced force
force diagram
friction
net force
unbalanced force

4. Force diagrams
In the diagram, what is the net force on the block? Record your answer in your notebook.

5. Read the introduction and look for key ideas

6. How can you tell if the forces on an object are balanced or unbalanced?

7. Describe the motion of the blocks that have been drawn
Discuss your answer with the class.

8. Complete the procedure and record your data
Be sure to pull the force meter gently so as not to damage the spring.

9. Analysis question 1
Describe an example and draw a force diagram of a situation with:
balanced forces.
unbalanced forces.

10. Analysis question 2
Imagine that a parked car is hit from the left with 30,000 N of force at the exact same time it is hit from the right with 40,000 N of force.
Draw a force diagram showing the two forces acting on the parked car.
Draw another force diagram showing only the net force on the parked car.

11. Analysis question 3
The force diagram below shows an object with zero net force, but there is one force missing. What is the missing force? Draw the diagram in your notebook, and complete it by drawing and labeling the missing force.

12. Analysis question 4
Look back at your work from Part A. Could the block in Part A have been moving? Explain.

13. Analysis question 5
For each situation in a-e below, explain why there is or is not a zero net force acting on the car.
A car is parked on a level parking space.
A traffic light turns green and a car starts to move.
A car drives steadily at 25 mph.
A car is slowing down from 30 mph to 10 mph.
A car goes around a corner at 10 mph.

14. Conclusion
When an object experiences a nonzero net force (unbalanced forces), some aspect of its acceleration – speed and/or direction of motion – will always change. Any object that is not traveling at a constant speed and direction must be in a situation where there is a nonzero net force (unbalanced forces) acting on it.

15. Conclusion
When an object experiences zero net force (balanced forces), its speed and direction of motion are constant. Any object traveling at a constant speed and direction, which could be either an object at rest or a moving object, has a zero net force (balanced forces).

16. How can you tell if the forces on an object are balanced or unbalanced?

17. Key vocabulary definitions
Balanced force - When the magnitude and direction of more then one force acting on an object results in zero net force. Force diagram - A simple labeled diagram that shows the forces acting on an object as arrows that indicate the magnitude and direction of the force.

18. Key vocabulary definitions
Friction - A force that exists at the boundary between any two objects that are in contact with each other. Net force - The combined force (magnitude and direction) acting on an object.

19. Key vocabulary definitions
Unbalanced force - When the magnitude and direction of more than one force acting on an object give a net force unequal to zero.