1. September 10
AP physics

2. Two forces act on a 6. 00-kg object. One of the forces is 10. 0 N
Two forces act on a 6.00-kg object. One of the forces is 10.0 N. If the object accelerates at 2.00 m/s2, what is the greatest possible magnitude of the other force?
a. 1.0 N
b. 2.0 N
c N
d N

3. Objective: To understand: Forces and pulleys Free body diagrams
Sum of the forces
Tension
Acceleration
Success Criteria
Be able to solve pulley problems

4. Pulley system Set up #1: Equal masses: Draw a diagram:
Examine the pulley system.
What do you notice?

5. Set up #2: Δm=50g
What do you notice?

6. Set up #3: Δm=100g
What do you notice?

7. Set up #4: Δm=50g total mass increased
What do you notice?

8. What can we say about pulleys?

9. Forces and pulleys Pulley rules:
Pulleys only change the direction of the forces.
Pulleys are frictionless
The do not add any force to the system

10. Strings don’t stretch Strings only pull Strings have no mass.
The acceleration of one body is the same as the other body only negative
Strings only pull
The direction of the force is always away from the object.
Strings have no mass.

11. Steps to solve a pulley problem:
Draw a free body diagram of each mass.
Sum the forces on each body separately
Solve for acceleration of each body.
Set the two accelerations equal and opposite.
Solve for Tension
Re-substitute to get acceleration

12. m1=4 kg
m2=8 kg
What is the tension?
What is the acceleration?

13. Solve for Tension
and acceleration
35 kg
50 kg

14. Practice: pulleys

15. Out: Draw a free body diagram of each mass:
What is the tension in the string?
What is the acceleration of the system?
m2=1.5kg
m1=4.5kg