Lecture 04-3: Compression Forces
Read Sections 4.7–4.8 in Matter & Interactions
Outline:
• Compression force
• Normal component (“normal force”)
• Parallel component (“friction”)
Tips for applying the Momentum Principle:
1. Draw a picture.
2. Define the system
3. Identify objects in the surroundings that interact with the system.
4. Draw a free-body diagram showing the forces.
5. Write the Momentum Principle
6. Substitute for the net force and the change in momentum. Solve for the unknown
algebraically.
Normal (component):
In the picture, an athlete is trying to lift a 90-kg barbell. Before the athlete touches the
barbell, what is the force by the floor on the barbell?
At the moment shown, the barbell remains at rest on the floor and the athlete is exerting
an upward force of 500 N. What is the normal force by the floor on the barbell?
Read Sections 4.7–4.8 in Matter & Interactions
Outline:
• Compression force
• Normal component (“normal force”)
• Parallel component (“friction”)
Tips for applying the Momentum Principle:
1. Draw a picture.
2. Define the system
3. Identify objects in the surroundings that interact with the system.
4. Draw a free-body diagram showing the forces.
5. Write the Momentum Principle
6. Substitute for the net force and the change in momentum. Solve for the unknown
algebraically.
Normal (component):
In the picture, an athlete is trying to lift a 90-kg barbell. Before the athlete touches the
barbell, what is the force by the floor on the barbell?
At the moment shown, the barbell remains at rest on the floor and the athlete is exerting
an upward force of 500 N. What is the normal force by the floor on the barbell?
