# September 10 AP physics.

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September 10 AP physics

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

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

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

Set up #2: Δm=50g What do you notice?

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

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

What can we say about pulleys?

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

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.

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

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

Solve for Tension and acceleration 35 kg 50 kg

Practice: pulleys

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