Linear Kinetics: Explaining the Causes of Linear Motion
Objectives
- Explain Newton's three laws of motion
- Apply Newton's second law of motion to determine the acceleration of an object if the forces acting on the object are known
- Apply Newton's second law of motion to determine the net force acting on an object if the acceleration of the object is known
- Define impulse
- Define momentum
- Explain the relationship between impulse and momentum
- Describe the relationship between mass and weight
Isaac Newton (1642-1727)
Newton's Laws of Motion
Conservation of Momentum
L=mv
Linear Kinetics: Explaining the Causes of Linear Motion
Objectives:
Money experiment (penny mass=2.5g, nickel=5.0g)
Elastic collisions: mava = mbvb
maua + mbub= mava + mbvb
Football collision
Coefficient of Restitution
Inelastic collisions: maua + mbub= mava + mb [e(ua - ub) + va]
Force affects motion
Measuring Ground Reaction Forces
Ground Reaction Forces in Walking and Running
Lunar Locomotion: How Large are the Forces?
F=ma
When Force is Changing:
Impulse = Favg Δ t
How do we calculate impulse?
Soccer Kick Example
How does this work in a spreadsheet?
Summary of Newton's Laws
First law: Inertia (resistance to a change in motion)
Second law: F=ma
Third law: Action-reaction
F=G(m1m2/r2)
F=ma or W=mg
How much does an astronaut weight?
Questions:
- Can a body be moving if no external forces are acting upon it?
- Can a body change its direction of motion if no external forces act on it?
- Can a body be moving with constant velocity if external forces are acting on it?
- If you pull on a tug of war rope with a force of 50 lb, how much force does the rope exert on you?
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