Choosing a Kinetic Analysis Method

 

We have studied three different kinetic analysis methods.

 

1. Newtonian mechanics
2. Work-energy method
3. Impulse-momentum method

 

Newtonian mechanics

 

∑F = ma

 

• Provides a relationship between forces and acceleration.
• Kinematic relationships must be employed to find velocity and position.

 

Work-energy method

 

U_1-2,non = ΔT + ΔV

 

• Provides a relationship between forces, displacement, and velocity directly.
• Only forces that do work must be considered.
• Can also determine instantaneous behavior by taking the time derivative of the work-energy balance equation.

 

Impulse-momentum method

 

∫∑F dt = ΔG

 

• The linear impulse-momentum principle provides a relationship between forces, time, and velocity.
• The linear impulse-momentum relationship is especially useful for analyzing collisions.

 

∫∑M_O = ΔH_O

 

• The angular impulse-momentum principle provides a relationship between moments, time, and velocity.
• The angular impulse-momentum relationship is especially useful for central-force problems.

 

Choosing a kinetic analysis method

 

Givens / Need to find	Most appropriate method
Forces / Acceleration	Newtonian Mechanics
Forces / Displacement / Velocity	Work-Energy
Forces / Time / Velocity	Linear Impulse-Momentum
Moments / Time / Velocity	Angular Impulse-Momentum